Messages in this thread Patch in this message | | | From | Amir Goldstein <> | Date | Mon, 15 Oct 2018 15:26:13 +0300 | Subject | Re: [LKP] [fsnotify] 60f7ed8c7c: will-it-scale.per_thread_ops -5.9% regression |
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On Mon, Oct 15, 2018 at 12:27 PM Amir Goldstein <amir73il@gmail.com> wrote: > > On Mon, Oct 15, 2018 at 10:50 AM Rong Chen <rong.a.chen@intel.com> wrote: > [...] > > the patch seems not work. > > > > tests: 1 > > testcase/path_params/tbox_group/run: will-it-scale/16-thread-unlink2-performance/lkp-bdw-ep3d > > > > commit: > > 1e6cb72399 ("fsnotify: add super block object type") > > 298cd0b2f4 (the below patch) > > > > 1e6cb72399fd58b3 298cd0b2f481d9cc2e2cd5bfd3 > > ---------------- -------------------------- > > %stddev change %stddev > > \ | \ > > 103.21 -5% 98.54 will-it-scale.time.user_time > > 46266 -6% 43516 will-it-scale.time.involuntary_context_switches > > 54483 -7% 50610 will-it-scale.per_thread_ops > > 871749 -7% 809765 will-it-scale.workload > > Thanks for testing my patch. As Jan commented, it is not surprising > that the patch > makes no difference. > > I would like to clarify a few things about how you ran the test before > I continue to > investigate: > > 1. When I ran the workload I saw that it writes files to whatever filesystem is > mounted on /tmp. Can I assume you have tmpfs mounted at /tmp? > > 2. Can you confirm that there is no fanotify mount mark on the /tmp mount? > for example: > # ls -l /proc/*/fd/*|grep fanotify > lrwx------ 1 root root 64 Oct 15 08:36 /proc/3927/fd/3 -> anon_inode:[fanotify] > # grep fanotify.mnt_id /proc/3927/fdinfo/3 > fanotify mnt_id:33 mflags:0 mask:3b ignored_mask:0 > # grep ^$(( 0x33 )) /proc/3927/mountinfo > 51 16 0:27 / /tmp rw,relatime shared:18 - tmpfs tmpfs rw > > 3. I saw that LKP caches the results for a specific commit > (i.e. 1e6cb72399 ("fsnotify: add super block object type")). > Did you use cached results when comparing to patch or did you re-run the > test with the "good" commit? The reason I am asking is because > sometimes performance result may differ between boots even with no > kernel code change. > Where all the "good" bisect samples taken from the same boot/machine? > or different boots/machines? > > 4. If this regression is reliably reproduced, then our best bet is on the > cost of access to s_fsnotify_{marks,mask} fields. > The patch below moves those frequently accessed fields near the > frequently accessed fields s_time_gran,s_writers and moves > the seldom accessed fields s_id,s_uuid further away. > Could you please try this patch? >
Better test this patch instead. It does a bit more re-organizing. If this works well for 16-thread-unlink2 workload, could you please also run it through other workloads to see if it improves them as well? and does not degrade them...
Thanks, Amir.
--- diff --git a/include/linux/fs.h b/include/linux/fs.h index 25a449f37bb1..baec0b3ff53f 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1393,17 +1393,24 @@ struct super_block {
struct sb_writers s_writers;
+ /* START frequently accessed fields block */ + void *s_fs_info; /* Filesystem private info */ + + /* Granularity of c/m/atime in ns (cannot be worse than a second) */ + u32 s_time_gran; +#ifdef CONFIG_FSNOTIFY + __u32 s_fsnotify_mask; + struct fsnotify_mark_connector __rcu *s_fsnotify_marks; +#endif + /* END frequently accessed fields block */ + + /* START seldom accessed fields block */ char s_id[32]; /* Informational name */ uuid_t s_uuid; /* UUID */
- void *s_fs_info; /* Filesystem private info */ unsigned int s_max_links; fmode_t s_mode;
- /* Granularity of c/m/atime in ns. - Cannot be worse than a second */ - u32 s_time_gran; - /* * The next field is for VFS *only*. No filesystems have any business * even looking at it. You had been warned. @@ -1415,6 +1422,7 @@ struct super_block { * in /proc/mounts will be "type.subtype" */ char *s_subtype; + /* END seldom accessed fields block */
const struct dentry_operations *s_d_op; /* default d_op for dentries */
@@ -1464,11 +1472,6 @@ struct super_block {
spinlock_t s_inode_wblist_lock; struct list_head s_inodes_wb; /* writeback inodes */ - -#ifdef CONFIG_FSNOTIFY - __u32 s_fsnotify_mask; - struct fsnotify_mark_connector __rcu *s_fsnotify_marks; -#endif } __randomize_layout;
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