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From: "NeilBrown" <neilb@suse.de>
To: "Christoph Hellwig" <hch@infradead.org>
Cc: "Trond Myklebust" <trond.myklebust@hammerspace.com>,
	"Anna Schumaker" <anna.schumaker@netapp.com>,
	"Chuck Lever" <chuck.lever@oracle.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Mel Gorman" <mgorman@suse.de>,
	linux-nfs@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH 12/13] MM: use AIO/DIO for reads from SWP_FS_OPS swap-space
Date: Wed, 17 Nov 2021 08:46:14 +1100	[thread overview]
Message-ID: <163709917463.13692.6685266362531701682@noble.neil.brown.name> (raw)
In-Reply-To: <YZNsf5yvfb8+SiqB@infradead.org>

On Tue, 16 Nov 2021, Christoph Hellwig wrote:
> On Tue, Nov 16, 2021 at 01:44:04PM +1100, NeilBrown wrote:
> > When pages a read from SWP_FS_OPS swap-space, the reads are submitted as
> > separate reads for each page.  This is generally less efficient than
> > larger reads.
> > 
> > We can use the block-plugging infrastructure to delay submitting the
> > read request until multiple contigious pages have been collected.  This
> > requires using ->direct_IO to submit the read (as ->readpages isn't
> > suitable for swap).
> 
> Abusing the block code here seems little ugly.  Also this won't
> compile if CONFIG_BLOCK is not set, will it?

There is nothing really block-layer-specific about the plugging
interfaces.  I think it would be quite reasonable to move them to lib/
But you are correct that currently without CONFIG_BLOCK the code will
compile but not work.

> 
> What is the problem with just batching up manually?

That would require a bigger change to common code, which would only
benefit one user.  The plugging mechanism works well for batching
requests to a block device.  Why not use it for non-block-devices too?

Thanks,
NeilBrown


> 
> > +	/* nofs needs as ->direct_IO may take the same mutex it takes for write */
> 
> Overly long line.
> 
> 

  reply	other threads:[~2021-11-16 21:46 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-16  2:44 [PATCH 00/13] Repair SWAP-over-NFS NeilBrown
2021-11-16  2:44 ` [PATCH 09/13] SUNRPC: improve 'swap' handling: scheduling and PF_MEMALLOC NeilBrown
2021-11-16  2:44 ` [PATCH 11/13] NFS: swap-out must always use STABLE writes NeilBrown
2021-11-16  2:44 ` [PATCH 02/13] NFS: do not take i_rwsem for swap IO NeilBrown
2021-11-16  7:52   ` Christoph Hellwig
2021-11-16 21:50     ` NeilBrown
2021-11-17  5:49       ` Christoph Hellwig
2021-11-16  2:44 ` [PATCH 08/13] NFS: discard NFS_RPC_SWAPFLAGS and RPC_TASK_ROOTCREDS NeilBrown
2021-11-16  2:44 ` [PATCH 01/13] NFS: move generic_write_checks() call from nfs_file_direct_write() to nfs_file_write() NeilBrown
2021-11-16  2:44 ` [PATCH 07/13] SUNRPC: remove scheduling boost for "SWAPPER" tasks NeilBrown
2021-11-16  2:44 ` [PATCH 10/13] NFSv4: keep state manager thread active if swap is enabled NeilBrown
2021-11-16  2:44 ` [PATCH 04/13] SUNRPC/call_alloc: async tasks mustn't block waiting for memory NeilBrown
2021-11-16  2:44 ` [PATCH 05/13] SUNRPC/auth: " NeilBrown
2021-11-16  2:44 ` [PATCH 13/13] MM: use AIO for DIO writes to swap NeilBrown
2021-11-16  2:44 ` [PATCH 06/13] SUNRPC/xprt: async tasks mustn't block waiting for memory NeilBrown
2021-11-16  2:44 ` [PATCH 03/13] MM: reclaim mustn't enter FS for swap-over-NFS NeilBrown
2021-11-16  8:32   ` Christoph Hellwig
2021-11-16 21:35     ` NeilBrown
2021-11-17  5:50       ` Christoph Hellwig
2021-11-18  1:43   ` kernel test robot
2021-11-18  1:43     ` kernel test robot
2021-11-16  2:44 ` [PATCH 12/13] MM: use AIO/DIO for reads from SWP_FS_OPS swap-space NeilBrown
2021-11-16  8:31   ` Christoph Hellwig
2021-11-16 21:46     ` NeilBrown [this message]
2021-11-16  3:29 ` [PATCH 00/13] Repair SWAP-over-NFS Matthew Wilcox
2021-11-16  3:55   ` NeilBrown

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