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Date: Wed, 27 Jul 2011 18:15:27 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Shaohua Li <shaohua.li@...el.com> Cc: Jens Axboe <jaxboe@...ionio.com>, Minchan Kim <minchan.kim@...il.com>, "mgorman@...e.de" <mgorman@...e.de>, linux-mm <linux-mm@...ck.org>, lkml <linux-kernel@...r.kernel.org> Subject: Re: [PATCH]vmscan: add block plug for page reclaim On Thu, 28 Jul 2011 09:04:20 +0800 Shaohua Li <shaohua.li@...el.com> wrote: > > Using an additional 44 bytes of stack on that path is also > > significant(ly bad). But we need to fix that problem anyway. One way > > we could improve things in mm/vmscan.c is to move the blk_plug into > > scan_control then get the scan_control off the stack in some manner. > > That's easy for kswapd: allocate one scan_control per kswapd at > > startup. Doing it for direct-reclaim would be a bit trickier... > unfortunately, the direct-reclaim case is what cares about stack. > > BTW, the scan_control can be dieted. may_unmap/may_swap/may_writepage > can be a bit. swappiness < 100, so can be a char. order <= 11, can be a > char. should I do it to cut the size? All five will fit in a 32-bit word, at some expense in code size. But I think first it would be better to work on a way of getting it all off the stack, along with the blk_plug. Could be done with a per-cpu array and CPU pinning, but CPU pinning is a bit expensive nowadays. Could put a scan_control* into the tack_struct, but that's dopey. -- 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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