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Date: Wed, 5 Nov 2008 17:07:48 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Chad Talbott <ctalbott@...gle.com> Cc: linux-kernel@...r.kernel.org, mrubin@...gle.com Subject: Re: Metadata in sys_sync_file_range and fadvise(DONTNEED) On Wed, 5 Nov 2008 16:56:54 -0800 Chad Talbott <ctalbott@...gle.com> wrote: > On Sat, Nov 1, 2008 at 1:21 AM, Andrew Morton <akpm@...ux-foundation.org> wrote: > > And fadvise(FADV_DONTNEED) is just that: "I won't be using that data > > again". Implementing specific writeback behaviour underneath that hint > > is unobvious and a bit weird. It's a bit of a fluke that it does > > writeout at all! > > > > We have much more flexibility with sync_file_range(), and it is more > > explicit. > > So in the new world, an application should call sync_file_range > (solving my problem by including metadata) to initiate writeout, and > then call posix_fadvise(DONTNEED) to drop the pages from page cache? > I think this would work for me. That would work. Although Nick is threatening to make sync_file_range(SYNC_FILE_RANGE_WRITE) all slow by using WB_SYNC_ALL, probably unnecessarily, ho hum. > > That being said, I don't understand why the IO scheduling problems > > which you're seeing are occurring. There is code in fs/mpage.c > > specifically to handle this case (search for "write_boundary_block"). > > It will spot that 4k indirect block in the middle of two 4MB data > > blocks and will schedule it for writeout at the right time. > > > > So why isn't that working? > > Very good question, I'll look into why it's not helping here. > Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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