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[pve-qemu-kvm.git] / debian / patches / 0007-use-extra-thread-for-vma-writer.patch

From 9cf799746fb3b21362fd62574cd76bfa14a24070 Mon Sep 17 00:00:00 2001
From: Dietmar Maurer <dietmar@proxmox.com>
Date: Mon, 14 Jan 2013 08:05:40 +0100
Subject: [PATCH v3 7/7] use extra thread for vma writer

The previous AIO approach has problem with bdrv_drain_all(), because writer
coroutines are not considered there. Those coroutines are not restarted, so
bdrv_drain_all() can fail (tracked_requests list not empty).

We now use a thread, so we could also add compression here.

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
---
 vma-writer.c |  296 +++++++++++++++++++++++++++++++++++-----------------------
 1 files changed, 180 insertions(+), 116 deletions(-)

diff --git a/vma-writer.c b/vma-writer.c
index 688af4b..e18591e 100644
--- a/vma-writer.c
+++ b/vma-writer.c
@@ -38,13 +38,20 @@
 
 #define WRITE_BUFFERS 5
 
-typedef struct VmaAIOCB VmaAIOCB;
-struct VmaAIOCB {
-    VmaWriter *vmaw;
+typedef struct WriteBuffer {
     unsigned char buffer[VMA_MAX_EXTENT_SIZE];
     size_t bytes;
-    Coroutine *co;
-};
+} WriteBuffer;
+
+typedef struct WriterThread {
+    int fd;
+    int error;
+    bool cancel;
+    GThread *thread;
+    GMutex *mutex;
+    GCond *change_cond;
+    WriteBuffer wbuf[WRITE_BUFFERS];
+} WriterThread;
 
 struct VmaWriter {
     int fd;
@@ -61,8 +68,7 @@ struct VmaWriter {
     int outbuf_count; /* in VMA_BLOCKS */
     uint64_t outbuf_block_info[VMA_BLOCKS_PER_EXTENT];
 
-    VmaAIOCB aiocbs[WRITE_BUFFERS];
-    CoQueue wqueue;
+    WriterThread wt;
 
     GChecksum *md5csum;
     CoMutex writer_lock;
@@ -88,6 +94,80 @@ struct VmaWriter {
     uint32_t config_count;
 };
 
+static gpointer vma_writer_thread(gpointer data)
+{
+    WriterThread *wt = (WriterThread *)data;
+
+    while (1) {
+        WriteBuffer *b = NULL;
+
+        g_mutex_lock(wt->mutex);
+        int i;
+        for (i = 0; i < WRITE_BUFFERS; i++) {
+            if (wt->wbuf[i].bytes) {
+                b = &wt->wbuf[i];
+                break;
+            }
+        }
+        g_mutex_unlock(wt->mutex);
+
+        if (b) {
+            size_t done = 0;
+            while (done < b->bytes) {
+                int ret = write(wt->fd, b->buffer + done, b->bytes - done);
+                if (ret > 0) {
+                    done += ret;
+                } else if (ret < 0) {
+                    if (!(errno == EAGAIN || errno == EWOULDBLOCK)) {
+                        g_mutex_lock(wt->mutex);
+                        wt->error = errno;
+                        g_mutex_unlock(wt->mutex);
+                        break;
+                    }
+                } else if (ret == 0) {
+                    /* should not happen - simply try again */
+                }
+            }
+            g_mutex_lock(wt->mutex);
+            b->bytes = 0;
+            g_mutex_unlock(wt->mutex);
+        }
+
+        if (wt->error) {
+            DPRINTF("WRITER THREAD ERROR %d - exit thread\n", wt->error);
+            g_thread_exit(NULL);
+        }
+
+        g_mutex_lock(wt->mutex);
+        bool cancel = wt->cancel;
+        if (!b && !cancel) {
+            g_cond_wait(wt->change_cond, wt->mutex);
+        }
+        g_mutex_unlock(wt->mutex);
+
+        if (cancel) {
+            DPRINTF("END WRITER THREAD\n");
+            g_thread_exit(NULL);
+        }
+    }
+
+    return NULL;
+}
+
+static void vma_stop_writer_thread(VmaWriter *vmaw)
+{
+    assert(vmaw);
+
+    if (vmaw->wt.thread) {
+        g_mutex_lock(vmaw->wt.mutex);
+        vmaw->wt.cancel = true;
+        g_cond_signal(vmaw->wt.change_cond);
+        g_mutex_unlock(vmaw->wt.mutex);
+        g_thread_join(vmaw->wt.thread);
+        vmaw->wt.thread = NULL;
+    }
+}
+
 void vma_writer_set_error(VmaWriter *vmaw, const char *fmt, ...)
 {
     va_list ap;
@@ -215,111 +295,47 @@ int vma_writer_register_stream(VmaWriter *vmaw, const char *devname,
     return n;
 }
 
-static void vma_co_continue_write(void *opaque)
-{
-    VmaWriter *vmaw = opaque;
-
-    qemu_aio_set_fd_handler(vmaw->fd, NULL, NULL, NULL, NULL);
-
-    DPRINTF("vma_co_continue_write\n");
-    qemu_coroutine_enter(vmaw->co_writer, NULL);
-}
-
-static ssize_t coroutine_fn
-vma_co_write(VmaWriter *vmaw, const void *buf, size_t bytes)
-{
-    size_t done = 0;
-    ssize_t ret;
-
-    /* atomic writes (we cannot interleave writes) */
-    qemu_co_mutex_lock(&vmaw->writer_lock);
-
-    DPRINTF("vma_co_write enter %zd\n", bytes);
-
-    while (done < bytes) {
-        ret = write(vmaw->fd, buf + done, bytes - done);
-        if (ret > 0) {
-            done += ret;
-            DPRINTF("vma_co_write written %zd %zd\n", done, ret);
-        } else if (ret < 0) {
-            if (errno == EAGAIN || errno == EWOULDBLOCK) {
-                DPRINTF("vma_co_write yield %zd\n", done);
-
-                vmaw->co_writer = qemu_coroutine_self();
-                qemu_aio_set_fd_handler(vmaw->fd, NULL, vma_co_continue_write,
-                                        NULL, vmaw);
-
-                qemu_coroutine_yield();
-                DPRINTF("vma_co_write restart %zd\n", done);
-            } else {
-                vma_writer_set_error(vmaw, "vma_co_write write error - %s",
-                                     strerror(errno));
-                done = -1; /* always return failure for partial writes */
-                break;
-            }
-        } else if (ret == 0) {
-            /* should not happen - simply try again */
-        }
-    }
-
-    qemu_co_mutex_unlock(&vmaw->writer_lock);
-
-    DPRINTF("vma_co_write leave %zd\n", done);
-    return done;
-}
-
-static void coroutine_fn vma_co_writer_task(void *opaque)
-{
-    VmaAIOCB *cb = opaque;
-
-    DPRINTF("vma_co_writer_task start\n");
-
-    int64_t done = vma_co_write(cb->vmaw, cb->buffer, cb->bytes);
-    DPRINTF("vma_co_writer_task write done %zd\n", done);
-
-    if (done != cb->bytes) {
-        DPRINTF("vma_co_writer_task failed write %zd %zd", cb->bytes, done);
-        vma_writer_set_error(cb->vmaw, "vma_co_writer_task failed write %zd",
-                             done);
-    }
-
-    cb->bytes = 0;
-
-    qemu_co_queue_next(&cb->vmaw->wqueue);
-
-    DPRINTF("vma_co_writer_task end\n");
-}
-
 static void coroutine_fn vma_queue_flush(VmaWriter *vmaw)
 {
     DPRINTF("vma_queue_flush enter\n");
 
     assert(vmaw);
 
+    int error;
+
     while (1) {
         int i;
-        VmaAIOCB *cb = NULL;
+        WriteBuffer *b = NULL;
+        g_mutex_lock(vmaw->wt.mutex);
+
+        error = vmaw->wt.error;
+
         for (i = 0; i < WRITE_BUFFERS; i++) {
-            if (vmaw->aiocbs[i].bytes) {
-                cb = &vmaw->aiocbs[i];
-                DPRINTF("FOUND USED AIO BUFFER %d %zd\n", i,
-                        vmaw->aiocbs[i].bytes);
+            if (vmaw->wt.wbuf[i].bytes) {
+                b = &vmaw->wt.wbuf[i];
+                DPRINTF("FOUND USED WRITE BUFFER %d %zd\n", i,
+                        vmaw->wt.wbuf[i].bytes);
                 break;
             }
         }
-        if (!cb) {
+        g_mutex_unlock(vmaw->wt.mutex);
+
+        if (!b || error) {
             break;
         }
-        qemu_co_queue_wait(&vmaw->wqueue);
+        uint64_t delay_ns = 10000;
+        DPRINTF("WAIT FOR BUFFER FLUSH %zd\n", delay_ns);
+        co_sleep_ns(rt_clock, delay_ns);
+    }
+
+    if (error) {
+        vma_writer_set_error(vmaw, "vma_queue_flush write error - %s",
+                             strerror(error));
     }
 
     DPRINTF("vma_queue_flush leave\n");
 }
 
-/**
- * NOTE: pipe buffer size in only 4096 bytes on linux (see 'ulimit -a')
- * So we need to create a coroutione to allow 'parallel' execution.
- */
 static ssize_t coroutine_fn
 vma_queue_write(VmaWriter *vmaw, const void *buf, size_t bytes)
 {
@@ -329,29 +345,46 @@ vma_queue_write(VmaWriter *vmaw, const void *buf, size_t bytes)
     assert(buf);
     assert(bytes <= VMA_MAX_EXTENT_SIZE);
 
-    VmaAIOCB *cb = NULL;
-    while (!cb) {
+    int error = 0;
+
+    /* wait for a free output buffer */
+    g_mutex_lock(vmaw->wt.mutex);
+    WriteBuffer *b = NULL;
+    while (!b) {
+        error = vmaw->wt.error;
+        if (error) {
+            g_mutex_unlock(vmaw->wt.mutex);
+            vma_writer_set_error(vmaw, "vma_queue_write error - %s",
+                                 strerror(error));
+            return -1;
+        }
+
         int i;
         for (i = 0; i < WRITE_BUFFERS; i++) {
-            if (!vmaw->aiocbs[i].bytes) {
-                cb = &vmaw->aiocbs[i];
+            if (!vmaw->wt.wbuf[i].bytes) {
+                b = &vmaw->wt.wbuf[i];
                 break;
             }
         }
-        if (!cb) {
-            qemu_co_queue_wait(&vmaw->wqueue);
+        if (!b) {
+            uint64_t delay_ns = 10000;
+            DPRINTF("WAIT FOR BUFFER %zd\n", delay_ns);
+            g_mutex_unlock(vmaw->wt.mutex);
+            co_sleep_ns(rt_clock, delay_ns);
+            g_mutex_lock(vmaw->wt.mutex);
         }
     }
 
-    memcpy(cb->buffer, buf, bytes);
-    cb->bytes = bytes;
-    cb->vmaw = vmaw;
+    /* copy data to output buffer */
+    memcpy(b->buffer, buf, bytes);
+    b->bytes = bytes;
+
+    /* signal writer thread that we have new data */
+    g_cond_signal(vmaw->wt.change_cond);
 
-    DPRINTF("vma_queue_write start %zd\n", bytes);
-    cb->co = qemu_coroutine_create(vma_co_writer_task);
-    qemu_coroutine_enter(cb->co, cb);
+    g_mutex_unlock(vmaw->wt.mutex);
 
-    DPRINTF("vma_queue_write leave\n");
+    DPRINTF("vma_queue_write queued %zd\n", bytes);
 
     return bytes;
 }
@@ -389,10 +422,10 @@ VmaWriter *vma_writer_create(const char *filename, uuid_t uuid, int64_t speed,
         const char *tmp_id_str;
 
         if ((stat(filename, &st) == 0) && S_ISFIFO(st.st_mode)) {
-            oflags = O_NONBLOCK|O_WRONLY;
+            oflags = O_WRONLY;
             vmaw->fd = qemu_open(filename, oflags, 0644);
         } else if (strstart(filename, "/dev/fdset/", &tmp_id_str)) {
-            oflags = O_NONBLOCK|O_WRONLY;
+            oflags = O_WRONLY;
             vmaw->fd = qemu_open(filename, oflags, 0644);
         } else if (strstart(filename, "/dev/fdname/", &tmp_id_str)) {
             vmaw->fd = monitor_get_fd(cur_mon, tmp_id_str, errp);
@@ -400,7 +433,7 @@ VmaWriter *vma_writer_create(const char *filename, uuid_t uuid, int64_t speed,
                 goto err;
             }
         } else  {
-            oflags = O_NONBLOCK|O_WRONLY|O_CREAT|O_EXCL;
+            oflags = O_WRONLY|O_CREAT|O_EXCL;
             vmaw->fd = qemu_open(filename, oflags, 0644);
         }
 
@@ -418,7 +451,6 @@ VmaWriter *vma_writer_create(const char *filename, uuid_t uuid, int64_t speed,
 
     qemu_co_mutex_init(&vmaw->writer_lock);
     qemu_co_mutex_init(&vmaw->flush_lock);
-    qemu_co_queue_init(&vmaw->wqueue);
 
     uuid_copy(vmaw->uuid, uuid);
 
@@ -428,6 +460,15 @@ VmaWriter *vma_writer_create(const char *filename, uuid_t uuid, int64_t speed,
 
     ratelimit_set_speed(&vmaw->limit, speed, 100000000ULL /* 0.1 sec */);
 
+    vmaw->wt.mutex = g_mutex_new();
+    vmaw->wt.change_cond = g_cond_new();
+    vmaw->wt.fd = vmaw->fd;
+    vmaw->wt.thread = g_thread_create(vma_writer_thread, &vmaw->wt, true, NULL);
+    if (vmaw->wt.thread == NULL) {
+        error_setg(errp, "can't allocate writer thread\n");
+        goto err;
+    }
+
     return vmaw;
 
 err:
@@ -442,6 +483,14 @@ err:
             g_checksum_free(vmaw->md5csum);
         }
 
+        if (vmaw->wt.mutex) {
+            g_mutex_free(vmaw->wt.mutex);
+        }
+
+        if (vmaw->wt.change_cond) {
+            g_cond_free(vmaw->wt.change_cond);
+        }
+
         g_free(vmaw);
     }
 
@@ -688,6 +737,16 @@ vma_writer_write(VmaWriter *vmaw, uint8_t dev_id, int64_t cluster_num,
 
     *zero_bytes = 0;
 
+    g_mutex_lock(vmaw->wt.mutex);
+    int error = vmaw->wt.error;
+    g_mutex_unlock(vmaw->wt.mutex);
+
+    if (error) {
+        vma_writer_set_error(vmaw, "vma_writer_get_buffer write error - %s",
+                             strerror(error));
+        return -1;
+    }
+
     if (vmaw->status < 0) {
         return vmaw->status;
     }
@@ -801,11 +860,7 @@ int vma_writer_close(VmaWriter *vmaw, Error **errp)
 
     vma_queue_flush(vmaw);
 
-    /* this should not happen - just to be sure */
-    while (!qemu_co_queue_empty(&vmaw->wqueue)) {
-        DPRINTF("vma_writer_close wait\n");
-        co_sleep_ns(rt_clock, 1000000);
-    }
+    vma_stop_writer_thread(vmaw);
 
     if (vmaw->cmd) {
         if (pclose(vmaw->cmd) < 0) {
@@ -851,8 +906,9 @@ void vma_writer_destroy(VmaWriter *vmaw)
 {
     assert(vmaw);
 
-    int i;
+    vma_stop_writer_thread(vmaw);
 
+    int i;
     for (i = 0; i <= 255; i++) {
         if (vmaw->stream_info[i].devname) {
             g_free(vmaw->stream_info[i].devname);
@@ -863,6 +919,14 @@ void vma_writer_destroy(VmaWriter *vmaw)
         g_checksum_free(vmaw->md5csum);
     }
 
+    if (vmaw->wt.mutex) {
+        g_mutex_free(vmaw->wt.mutex);
+    }
+
+    if (vmaw->wt.change_cond) {
+        g_cond_free(vmaw->wt.change_cond);
+    }
+
     g_free(vmaw);
 }
 
-- 
1.7.2.5