From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E8B71F78E6 for ; Mon, 24 Feb 2025 19:13:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740424426; cv=none; b=GzXjdcht5Am8MelDT3go/gtw1GoEMEHgQdRgWbYJSi60yzv+lgkshYfjoFo5lMB7KjkHay2T/AFQDRbbMAlDTR+rNVQrPaaNzeDNF5h0PHtz+G9uJuC1RCgWTOTsWCvgcyms4Tr/FPikdTyNafrOyzYHH7Dz08pab2NxuMcYC/I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740424426; c=relaxed/simple; bh=etQI8p2cL5nDJAE2eWoRVCwgozvW2w6+Y0oa+bYaNUs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=j9VK4cf/8N32w6GMTz6Pa9/FSTts45Mp0Gm7wZzPm9qemyhMIhXG0AcEnhkPgeBwdlq3rlkn1ZyrAYwbU0F8VrMBBljECjnMxxBq7P4oTLwPEGPg8uls+dUBvZ/DluH7b8pF6+CBF0FIqJgnT9FJIroVQFdN6M9h7g3J82QVlE4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ThTg68DX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ThTg68DX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74B0AC4CEE7; Mon, 24 Feb 2025 19:13:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1740424425; bh=etQI8p2cL5nDJAE2eWoRVCwgozvW2w6+Y0oa+bYaNUs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ThTg68DXZlf6qVMxkGNK9EySAl5PBSD+AKCCrGFLkrX/bvonUkigJHRLrcoir7rkQ 6rY0npo29X5pHZRFaDuAUhB51krGktDTqMiC9zKFkV879vtiuTMmrrV17Sd7cEuijI RSZJbA5cKGOaLrFmoAK9C7j/udGfm5qgB2j/TqKPyXgRVfIHUK/wmvdVLdMLSygXMg lMB0ytp6GNQrCeYUEJtLXS2/NFIj5sPwfUC7Rx1/YBMzgYSHPgaA9W8M35a1uP33cB Q9RsZmJthp7utCXbzOdT9/OlbQ+fBZgLIMK0WPxPVJj8jnGIL/eOwJ7cHU7UJ78J5X ky74QSrZgOopw== Date: Mon, 24 Feb 2025 11:13:45 -0800 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Carlos Maiolino , linux-xfs@vger.kernel.org Subject: Re: [PATCH 1/4] xfs: reduce context switches for synchronous buffered I/O Message-ID: <20250224191345.GA21808@frogsfrogsfrogs> References: <20250224151144.342859-1-hch@lst.de> <20250224151144.342859-2-hch@lst.de> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250224151144.342859-2-hch@lst.de> On Mon, Feb 24, 2025 at 07:11:35AM -0800, Christoph Hellwig wrote: > Currently all metadata I/O completions happen in the m_buf_workqueue > workqueue. But for synchronous I/O (i.e. all buffer reads) there is no > need for that, as there always is a called in process context that is > waiting for the I/O. Factor out the guts of xfs_buf_ioend into a > separate helper and call it from xfs_buf_iowait to avoid a double > an extra context switch to the workqueue. > > Signed-off-by: Christoph Hellwig > --- > fs/xfs/xfs_buf.c | 43 +++++++++++++++++++++++++++---------------- > 1 file changed, 27 insertions(+), 16 deletions(-) > > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c > index 15bb790359f8..821aa85e2ce5 100644 > --- a/fs/xfs/xfs_buf.c > +++ b/fs/xfs/xfs_buf.c > @@ -1345,6 +1345,7 @@ xfs_buf_ioend_handle_error( > resubmit: > xfs_buf_ioerror(bp, 0); > bp->b_flags |= (XBF_DONE | XBF_WRITE_FAIL); > + reinit_completion(&bp->b_iowait); > xfs_buf_submit(bp); > return true; > out_stale: > @@ -1355,8 +1356,9 @@ xfs_buf_ioend_handle_error( > return false; > } > > -static void > -xfs_buf_ioend( > +/* returns false if the caller needs to resubmit the I/O, else false */ "...else true" ? --D > +static bool > +__xfs_buf_ioend( > struct xfs_buf *bp) > { > trace_xfs_buf_iodone(bp, _RET_IP_); > @@ -1376,7 +1378,7 @@ xfs_buf_ioend( > } > > if (unlikely(bp->b_error) && xfs_buf_ioend_handle_error(bp)) > - return; > + return false; > > /* clear the retry state */ > bp->b_last_error = 0; > @@ -1397,7 +1399,15 @@ xfs_buf_ioend( > > bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD | > _XBF_LOGRECOVERY); > + return true; > +} > > +static void > +xfs_buf_ioend( > + struct xfs_buf *bp) > +{ > + if (!__xfs_buf_ioend(bp)) > + return; > if (bp->b_flags & XBF_ASYNC) > xfs_buf_relse(bp); > else > @@ -1411,15 +1421,8 @@ xfs_buf_ioend_work( > struct xfs_buf *bp = > container_of(work, struct xfs_buf, b_ioend_work); > > - xfs_buf_ioend(bp); > -} > - > -static void > -xfs_buf_ioend_async( > - struct xfs_buf *bp) > -{ > - INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work); > - queue_work(bp->b_mount->m_buf_workqueue, &bp->b_ioend_work); > + if (__xfs_buf_ioend(bp)) > + xfs_buf_relse(bp); > } > > void > @@ -1491,7 +1494,13 @@ xfs_buf_bio_end_io( > XFS_TEST_ERROR(false, bp->b_mount, XFS_ERRTAG_BUF_IOERROR)) > xfs_buf_ioerror(bp, -EIO); > > - xfs_buf_ioend_async(bp); > + if (bp->b_flags & XBF_ASYNC) { > + INIT_WORK(&bp->b_ioend_work, xfs_buf_ioend_work); > + queue_work(bp->b_mount->m_buf_workqueue, &bp->b_ioend_work); > + } else { > + complete(&bp->b_iowait); > + } > + > bio_put(bio); > } > > @@ -1568,9 +1577,11 @@ xfs_buf_iowait( > { > ASSERT(!(bp->b_flags & XBF_ASYNC)); > > - trace_xfs_buf_iowait(bp, _RET_IP_); > - wait_for_completion(&bp->b_iowait); > - trace_xfs_buf_iowait_done(bp, _RET_IP_); > + do { > + trace_xfs_buf_iowait(bp, _RET_IP_); > + wait_for_completion(&bp->b_iowait); > + trace_xfs_buf_iowait_done(bp, _RET_IP_); > + } while (!__xfs_buf_ioend(bp)); > > return bp->b_error; > } > -- > 2.45.2 > >