| Message ID | 20170629030151.1672771-1-terrelln@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jun 28, 2017 at 08:01:51PM -0700, Nick Terrell wrote: > > Is there a version I should be testing? > > Not yet, I'm working on v2 of the patch set, which will be ready soon. > > > I got a bunch of those: > > [10170.448783] kworker/u8:6: page allocation stalls for 60720ms, order:0, mode:0x14000c2(GFP_KERNEL|__GFP_HIGHMEM), nodemask=(null) > > [10170.448819] kworker/u8:6 cpuset=/ mems_allowed=0 > > [10170.448842] CPU: 3 PID: 13430 Comm: kworker/u8:6 Not tainted 4.12.0-rc7-00034-gdff47ed160bb #1 > > [10170.448846] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) > > [10170.448872] Workqueue: btrfs-endio btrfs_endio_helper > > [10170.448910] [<c010de1c>] (unwind_backtrace) from [<c010adb8>] (show_stack+0x10/0x14) > > [10170.448925] [<c010adb8>] (show_stack) from [<c0442b00>] (dump_stack+0x78/0x8c) > > [10170.448942] [<c0442b00>] (dump_stack) from [<c01b0178>] (warn_alloc+0xc0/0x170) > > [10170.448952] [<c01b0178>] (warn_alloc) from [<c01b0c3c>] (__alloc_pages_nodemask+0x97c/0xe30) > > [10170.448964] [<c01b0c3c>] (__alloc_pages_nodemask) from [<c01e217c>] (__vmalloc_node_range+0x144/0x27c) > > [10170.448976] [<c01e217c>] (__vmalloc_node_range) from [<c01e2550>] (__vmalloc_node.constprop.10+0x48/0x50) > > [10170.448982] [<c01e2550>] (__vmalloc_node.constprop.10) from [<c01e25ec>] (vmalloc+0x2c/0x34) > > [10170.448990] [<c01e25ec>] (vmalloc) from [<c038f7cc>] (zstd_alloc_workspace+0x6c/0xb8) > > [10170.448997] [<c038f7cc>] (zstd_alloc_workspace) from [<c038fcb8>] (find_workspace+0x120/0x1f4) > > [10170.449002] [<c038fcb8>] (find_workspace) from [<c038ff60>] (end_compressed_bio_read+0x1d4/0x3b0) > > [10170.449016] [<c038ff60>] (end_compressed_bio_read) from [<c0130e14>] (process_one_work+0x1d8/0x3f0) > > [10170.449026] [<c0130e14>] (process_one_work) from [<c0131a18>] (worker_thread+0x38/0x558) > > [10170.449035] [<c0131a18>] (worker_thread) from [<c0136854>] (kthread+0x124/0x154) > > [10170.449042] [<c0136854>] (kthread) from [<c01076f8>] (ret_from_fork+0x14/0x3c) > > > > which never happened with compress=lzo, and a 2GB RAM machine that runs 4 > > threads of various builds runs into memory pressure quite often. On the > > other hand, I used 4.11 for lzo so this needs more testing before I can > > blame the zstd code. > > I'm not sure what is causing the symptom of stalls in vmalloc(), but I > think I know what is causing vmalloc() to be called so often. Its probably > showing up for zstd and not lzo because it requires more memory. > > find_workspace() allocates up to num_online_cpus() + 1 workspaces. > free_workspace() will only keep num_online_cpus() workspaces. When > (de)compressing we will allocate num_online_cpus() + 1 workspaces, then > free one, and repeat. Instead, we can just keep num_online_cpus() + 1 > workspaces around, and never have to allocate/free another workspace in the > common case. That would be much better and probably was the original intention. And I guess improves performance when we don't have to do the extra alloc/free rounds. > I tested on a Ubuntu 14.04 VM with 2 cores and 4 GiB of RAM. I mounted a > BtrFS partition with -o compress-force={lzo,zlib,zstd} and logged whenever > a workspace was allocated of freed. Then I copied vmlinux (527 MB) to the > partition. Before the patch, during the copy it would allocate and free 5-6 > workspaces. After, it only allocated the initial 3. This held true for lzo, > zlib, and zstd. > > > I'm on linus:4.12-rc7 with only a handful of btrfs patches (v3 of Qu's chunk > > check, some misc crap) -- I guess I should use at least btrfs-for-4.13. Or > > would you prefer full-blown next? > > Whatever is convenient for you. The relevant code in BtrFS hasn't changed > for a few months, so it shouldn't matter too much. > > Signed-off-by: Nick Terrell <terrelln@fb.com> > --- > fs/btrfs/compression.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c > index 3beb0d0..1a0ef55 100644 > --- a/fs/btrfs/compression.c > +++ b/fs/btrfs/compression.c > @@ -874,7 +874,7 @@ static void free_workspace(int type, struct list_head *workspace) > int *free_ws = &btrfs_comp_ws[idx].free_ws; > > spin_lock(ws_lock); > - if (*free_ws < num_online_cpus()) { > + if (*free_ws <= num_online_cpus()) { > list_add(workspace, idle_ws); > (*free_ws)++; > spin_unlock(ws_lock); Please send it as a proper patch, thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 3beb0d0..1a0ef55 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -874,7 +874,7 @@ static void free_workspace(int type, struct list_head *workspace) int *free_ws = &btrfs_comp_ws[idx].free_ws; spin_lock(ws_lock); - if (*free_ws < num_online_cpus()) { + if (*free_ws <= num_online_cpus()) { list_add(workspace, idle_ws); (*free_ws)++; spin_unlock(ws_lock);