projects / mirror_zfs-debian.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c82c597 CIK |
1 | Increase default zcmd allocation to 256K (LP: #567557) |
| 2 | ||
| 3 | When creating hundreds of clones (for example using containers with | |
| 4 | LXD) cloning slows down as the number of clones increases over time. | |
| 5 | The reason for this is that the fetching of the clone information | |
| 6 | using a small zcmd buffer requires two ioctl calls, one to determine | |
| 7 | the size and a second to return the data. However, this requires | |
| 8 | gathering the data twice, once to determine the size and again to | |
| 9 | populate the zcmd buffer to return it to userspace. | |
| 10 | ||
| 11 | These are expensive ioctl() calls, so instead, make the default buffer | |
| 12 | size much larger: 256K. This may sound large, but on 64 bit systems | |
| 13 | running ZFS this is not a huge chunk of memory for the speed | |
| 14 | improvement we gains for large sets of clones: | |
| 15 | ||
| 16 | 16K zcmd 256K zcmd | |
| 17 | Clones Time Clones Time Clone % improvement | |
| 18 | (secs) per sec (secs) per sec | |
| 19 | 100 7 14.29 5 20.00 28.57 | |
| 20 | 200 10 20.00 9 22.22 10.00 | |
| 21 | 300 19 15.79 18 16.67 5.26 | |
| 22 | 400 22 18.18 22 18.18 0.00 | |
| 23 | 500 29 17.24 29 17.24 0.00 | |
| 24 | 600 39 15.38 39 15.38 0.00 | |
| 25 | 700 46 15.22 45 15.56 2.17 | |
| 26 | 800 58 13.79 51 15.69 12.07 | |
| 27 | 900 74 12.16 61 14.75 17.57 | |
| 28 | 1000 90 11.11 74 13.51 17.78 | |
| 29 | 1100 98 11.22 87 12.64 11.22 | |
| 30 | 1200 102 11.76 95 12.63 6.86 | |
| 31 | 1300 113 11.50 104 12.50 7.96 | |
| 32 | 1400 143 9.79 109 12.84 23.78 | |
| 33 | 1500 145 10.34 132 11.36 8.97 | |
| 34 | 1600 165 9.70 145 11.03 12.12 | |
| 35 | 1700 187 9.09 156 10.90 16.58 | |
| 36 | 1800 210 8.57 166 10.84 20.95 | |
| 37 | 1900 226 8.41 183 10.38 19.03 | |
| 38 | 2000 256 7.81 198 10.10 22.66 | |
| 39 | 2200 311 7.07 238 9.24 23.47 | |
| 40 | 2400 373 6.43 271 8.86 27.35 | |
| 41 | 2600 487 5.34 316 8.23 35.11 | |
| 42 | 3000 619 4.85 426 7.04 31.18 | |
| 43 | 3400 915 3.72 549 6.19 40.00 | |
| 44 | 4000 1332 3.00 923 4.33 30.71 | |
| 45 | ||
| 46 | As one can see, with > 2000 clones we get 25-40% speed | |
| 47 | improvement. | |
| 48 | ||
| 49 | This patch was originally suggested by Brian Behlendorf | |
| 50 | (see https://github.com/zfsonlinux/zfs/issues/6372), however | |
| 51 | this fix is a more generic fix to cover all zcmd cases. | |
| 52 | ||
| 53 | Signed-off-by: Colin Ian King <colin.king@canonical.com> | |
| 54 | ||
| 55 | Index: zfs/lib/libzfs/libzfs_util.c | |
| 56 | =================================================================== | |
| 57 | --- zfs.orig/lib/libzfs/libzfs_util.c | |
| 58 | +++ zfs/lib/libzfs/libzfs_util.c | |
| 59 | @@ -1354,7 +1354,7 @@ int | |
| 60 | zcmd_alloc_dst_nvlist(libzfs_handle_t *hdl, zfs_cmd_t *zc, size_t len) | |
| 61 | { | |
| 62 | if (len == 0) | |
| 63 | - len = 16 * 1024; | |
| 64 | + len = 256 * 1024; | |
| 65 | zc->zc_nvlist_dst_size = len; | |
| 66 | zc->zc_nvlist_dst = | |
| 67 | (uint64_t)(uintptr_t)zfs_alloc(hdl, zc->zc_nvlist_dst_size); |