From: David Howells <dhowells@redhat.com>
To: Christian Brauner <christian@brauner.io>,
Matthew Wilcox <willy@infradead.org>
Cc: dhowells@redhat.com, Jeff Layton <jlayton@kernel.org>,
Gao Xiang <hsiangkao@linux.alibaba.com>,
Dominique Martinet <asmadeus@codewreck.org>,
Steve French <smfrench@gmail.com>,
Marc Dionne <marc.dionne@auristor.com>,
Paulo Alcantara <pc@manguebit.com>,
Shyam Prasad N <sprasad@microsoft.com>,
Tom Talpey <tom@talpey.com>,
Eric Van Hensbergen <ericvh@kernel.org>,
Ilya Dryomov <idryomov@gmail.com>,
netfs@lists.linux.dev, linux-cachefs@redhat.com,
linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org,
linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org,
v9fs@lists.linux.dev, linux-erofs@lists.ozlabs.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Latchesar Ionkov <lucho@ionkov.net>,
Christian Schoenebeck <linux_oss@crudebyte.com>
Subject: Re: [PATCH 23/26] netfs: Cut over to using new writeback code
Date: Mon, 08 Apr 2024 16:53:17 +0100 [thread overview]
Message-ID: <877902.1712591597@warthog.procyon.org.uk> (raw)
In-Reply-To: <20240328163424.2781320-24-dhowells@redhat.com>
David Howells <dhowells@redhat.com> wrote:
> + /* Wait for writeback to complete. The writeback engine owns
> + * the info in folio->private and may change it until it
> + * removes the WB mark.
> + */
> + if (folio_wait_writeback_killable(folio)) {
> + ret = written ? -EINTR : -ERESTARTSYS;
> + goto error_folio_unlock;
> + }
> +
It turns out that this really kills performance with fio with as many jobs as
cpus. It's taking up to around 8x longer to complete a pwrite() on average
and perf shows a 30% of the CPU cycles are being spent in contention on the
i_rwsem.
The reason this was added here is that writeback cannot take the folio lock in
order to clean up folio->private without risking deadlock vs the truncation
routines (IIRC).
I can mitigate this by skipping the wait if folio->private is not set and if
we're not going to attach anything there (see attached). Note that if
writeout is ongoing and there is nothing attached to ->private, then we should
not be engaging write-streaming mode and attaching a new netfs_folio (and if
we did, we'd flush the page and wait for it anyway).
The other possibility is if we have a writeback group to set. This only
applies to ceph for the moment and is something that will need dealing with
if/when ceph is made to use this code.
David
---
diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 1eff9413eb1b..279b296f8014 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -255,7 +255,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
* the info in folio->private and may change it until it
* removes the WB mark.
*/
- if (folio_wait_writeback_killable(folio)) {
+ if (folio_get_private(folio) &&
+ folio_wait_writeback_killable(folio)) {
ret = written ? -EINTR : -ERESTARTSYS;
goto error_folio_unlock;
}
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com>
To: Christian Brauner <christian@brauner.io>,
Matthew Wilcox <willy@infradead.org>
Cc: Latchesar Ionkov <lucho@ionkov.net>,
Dominique Martinet <asmadeus@codewreck.org>,
Christian Schoenebeck <linux_oss@crudebyte.com>,
dhowells@redhat.com, linux-mm@kvack.org,
Marc Dionne <marc.dionne@auristor.com>,
linux-afs@lists.infradead.org, Paulo Alcantara <pc@manguebit.com>,
linux-cifs@vger.kernel.org, Steve French <smfrench@gmail.com>,
linux-cachefs@redhat.com, Gao Xiang <hsiangkao@linux.alibaba.com>,
Ilya Dryomov <idryomov@gmail.com>,
Shyam Prasad N <sprasad@microsoft.com>,
Tom Talpey <tom@talpey.com>,
ceph-devel@vger.kernel.org,
Eric Van Hensbergen <ericvh@kernel.org>,
linux-nfs@vger.kernel.org, netdev@vger.kernel.org,
v9fs@lists.linux.dev, Jeff Layton <jlayton@kernel.org>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
netfs@lists.linux.dev, linux-erofs@lists.ozlabs.org
Subject: Re: [PATCH 23/26] netfs: Cut over to using new writeback code
Date: Mon, 08 Apr 2024 16:53:17 +0100 [thread overview]
Message-ID: <877902.1712591597@warthog.procyon.org.uk> (raw)
In-Reply-To: <20240328163424.2781320-24-dhowells@redhat.com>
David Howells <dhowells@redhat.com> wrote:
> + /* Wait for writeback to complete. The writeback engine owns
> + * the info in folio->private and may change it until it
> + * removes the WB mark.
> + */
> + if (folio_wait_writeback_killable(folio)) {
> + ret = written ? -EINTR : -ERESTARTSYS;
> + goto error_folio_unlock;
> + }
> +
It turns out that this really kills performance with fio with as many jobs as
cpus. It's taking up to around 8x longer to complete a pwrite() on average
and perf shows a 30% of the CPU cycles are being spent in contention on the
i_rwsem.
The reason this was added here is that writeback cannot take the folio lock in
order to clean up folio->private without risking deadlock vs the truncation
routines (IIRC).
I can mitigate this by skipping the wait if folio->private is not set and if
we're not going to attach anything there (see attached). Note that if
writeout is ongoing and there is nothing attached to ->private, then we should
not be engaging write-streaming mode and attaching a new netfs_folio (and if
we did, we'd flush the page and wait for it anyway).
The other possibility is if we have a writeback group to set. This only
applies to ceph for the moment and is something that will need dealing with
if/when ceph is made to use this code.
David
---
diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
index 1eff9413eb1b..279b296f8014 100644
--- a/fs/netfs/buffered_write.c
+++ b/fs/netfs/buffered_write.c
@@ -255,7 +255,8 @@ ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
* the info in folio->private and may change it until it
* removes the WB mark.
*/
- if (folio_wait_writeback_killable(folio)) {
+ if (folio_get_private(folio) &&
+ folio_wait_writeback_killable(folio)) {
ret = written ? -EINTR : -ERESTARTSYS;
goto error_folio_unlock;
}
next prev parent reply other threads:[~2024-04-08 15:53 UTC|newest]
Thread overview: 125+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-28 16:33 [PATCH 00/26] netfs, afs, 9p, cifs: Rework netfs to use ->writepages() to copy to cache David Howells
2024-03-28 16:33 ` David Howells
2024-03-28 16:33 ` [PATCH 01/26] cifs: Fix duplicate fscache cookie warnings David Howells
2024-03-28 16:33 ` David Howells
2024-04-15 11:25 ` Jeff Layton
2024-04-15 11:25 ` Jeff Layton
2024-04-15 13:03 ` David Howells
2024-04-15 13:03 ` David Howells
2024-04-15 22:51 ` Steve French
2024-04-15 22:51 ` Steve French
2024-04-16 22:40 ` David Howells
2024-04-16 22:40 ` David Howells
2024-03-28 16:33 ` [PATCH 02/26] 9p: Clean up some kdoc and unused var warnings David Howells
2024-03-28 16:33 ` David Howells
2024-03-28 16:33 ` [PATCH 03/26] netfs: Update i_blocks when write committed to pagecache David Howells
2024-03-28 16:33 ` David Howells
2024-04-15 11:28 ` Jeff Layton
2024-04-15 11:28 ` Jeff Layton
2024-04-16 22:47 ` David Howells
2024-04-16 22:47 ` David Howells
2024-03-28 16:33 ` [PATCH 04/26] netfs: Replace PG_fscache by setting folio->private and marking dirty David Howells
2024-03-28 16:33 ` David Howells
2024-03-28 16:33 ` [PATCH 05/26] mm: Remove the PG_fscache alias for PG_private_2 David Howells
2024-03-28 16:33 ` David Howells
2024-03-28 16:33 ` [PATCH 06/26] netfs: Remove deprecated use of PG_private_2 as a second writeback flag David Howells
2024-03-28 16:33 ` David Howells
2024-03-28 16:33 ` [PATCH 07/26] netfs: Make netfs_io_request::subreq_counter an atomic_t David Howells
2024-03-28 16:33 ` David Howells
2024-03-28 16:34 ` [PATCH 08/26] netfs: Use subreq_counter to allocate subreq debug_index values David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 09/26] mm: Provide a means of invalidation without using launder_folio David Howells
2024-03-28 16:34 ` David Howells
2024-04-15 11:41 ` Jeff Layton
2024-04-15 11:41 ` Jeff Layton
2024-04-17 9:02 ` David Howells
2024-03-28 16:34 ` [PATCH 10/26] cifs: Use alternative invalidation to " David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 11/26] 9p: " David Howells
2024-03-28 16:34 ` David Howells
2024-04-15 11:43 ` Jeff Layton
2024-04-15 11:43 ` Jeff Layton
2024-04-16 23:03 ` David Howells
2024-04-16 23:03 ` David Howells
2024-03-28 16:34 ` [PATCH 12/26] afs: " David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 13/26] netfs: Remove ->launder_folio() support David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 14/26] netfs: Use mempools for allocating requests and subrequests David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 15/26] mm: Export writeback_iter() David Howells
2024-03-28 16:34 ` David Howells
2024-04-03 8:59 ` Christoph Hellwig
2024-04-03 8:59 ` Christoph Hellwig
2024-04-03 10:10 ` David Howells
2024-04-03 10:10 ` David Howells
2024-04-03 10:14 ` Christoph Hellwig
2024-04-03 10:14 ` Christoph Hellwig
2024-04-03 10:55 ` David Howells
2024-04-03 10:55 ` David Howells
2024-04-03 12:41 ` Christoph Hellwig
2024-04-03 12:41 ` Christoph Hellwig
2024-04-03 12:58 ` David Howells
2024-04-03 12:58 ` David Howells
2024-04-05 6:53 ` Christoph Hellwig
2024-04-05 6:53 ` Christoph Hellwig
2024-04-05 10:15 ` Christian Brauner
2024-04-05 10:15 ` Christian Brauner
2024-03-28 16:34 ` [PATCH 16/26] netfs: Switch to using unsigned long long rather than loff_t David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 17/26] netfs: Fix writethrough-mode error handling David Howells
2024-03-28 16:34 ` David Howells
2024-04-15 12:40 ` Jeff Layton
2024-04-15 12:40 ` Jeff Layton
2024-04-17 9:04 ` David Howells
2024-04-17 9:04 ` David Howells
2024-03-28 16:34 ` [PATCH 18/26] netfs: Add some write-side stats and clean up some stat names David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 19/26] netfs: New writeback implementation David Howells
2024-03-28 16:34 ` David Howells
2024-03-29 10:34 ` Naveen Mamindlapalli
2024-03-29 10:34 ` Naveen Mamindlapalli
2024-03-30 1:06 ` Vadim Fedorenko
2024-03-30 1:06 ` Vadim Fedorenko
2024-03-30 1:06 ` Vadim Fedorenko
2024-03-30 1:06 ` Vadim Fedorenko
2024-03-30 1:03 ` Vadim Fedorenko
2024-03-30 1:03 ` Vadim Fedorenko
2024-03-28 16:34 ` [PATCH 20/26] netfs, afs: Implement helpers for new write code David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 21/26] netfs, 9p: " David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 22/26] netfs, cachefiles: " David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 23/26] netfs: Cut over to using new writeback code David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 24/26] netfs: Remove the old " David Howells
2024-03-28 16:34 ` David Howells
2024-04-15 12:20 ` Jeff Layton
2024-04-15 12:20 ` Jeff Layton
2024-04-17 10:36 ` David Howells
2024-04-17 10:36 ` David Howells
2024-03-28 16:34 ` [PATCH 25/26] netfs: Miscellaneous tidy ups David Howells
2024-03-28 16:34 ` David Howells
2024-03-28 16:34 ` [PATCH 26/26] netfs, afs: Use writeback retry to deal with alternate keys David Howells
2024-03-28 16:34 ` David Howells
2024-04-01 13:53 ` Simon Horman
2024-04-01 13:53 ` Simon Horman
2024-04-02 8:32 ` David Howells
2024-04-02 8:32 ` David Howells
2024-04-10 17:38 ` Simon Horman
2024-04-10 17:38 ` Simon Horman
2024-04-11 7:09 ` David Howells
2024-04-11 7:09 ` David Howells
2024-04-02 8:46 ` [PATCH 19/26] netfs: New writeback implementation David Howells
2024-04-02 8:46 ` David Howells
2024-04-02 10:48 ` [PATCH 00/26] netfs, afs, 9p, cifs: Rework netfs to use ->writepages() to copy to cache Christian Brauner
2024-04-02 10:48 ` Christian Brauner
2024-04-04 7:51 ` [PATCH 21/26] netfs, 9p: Implement helpers for new write code David Howells
2024-04-04 7:51 ` David Howells
2024-04-04 8:01 ` David Howells
2024-04-04 8:01 ` David Howells
2024-04-08 15:53 ` David Howells [this message]
2024-04-08 15:53 ` [PATCH 23/26] netfs: Cut over to using new writeback code David Howells
2024-04-15 12:49 ` [PATCH 00/26] netfs, afs, 9p, cifs: Rework netfs to use ->writepages() to copy to cache Jeff Layton
2024-04-15 12:49 ` Jeff Layton
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