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Message-ID: <200608190612_MC3-1-C895-98A8@compuserve.com> Date: Sat, 19 Aug 2006 06:11:34 -0400 From: Chuck Ebbert <76306.1226@...puserve.com> To: linux-kernel <linux-kernel@...r.kernel.org> Cc: Jens Axboe <axboe@...e.de>, Andi Kleen <ak@...e.de> Subject: [patch] block: fix queue bounce limit calculation Queue bounce should start after the max page, not on it. Signed-off-by: Chuck Ebbert <76306.1226@...puserve.com> --- Could this explain reported slowdown on x86_64 after limit was changed in 2.6.16.7? --- 2.6.17.9-64.orig/block/ll_rw_blk.c +++ 2.6.17.9-64/block/ll_rw_blk.c @@ -638,11 +638,11 @@ void blk_queue_bounce_limit(request_queu /* Assume anything <= 4GB can be handled by IOMMU. Actually some IOMMUs can handle everything, but I don't know of a way to test this here. */ - if (bounce_pfn < (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) + if (bounce_pfn <= (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) dma = 1; q->bounce_pfn = max_low_pfn; #else - if (bounce_pfn < blk_max_low_pfn) + if (bounce_pfn <= blk_max_low_pfn) dma = 1; q->bounce_pfn = bounce_pfn; #endif -- Chuck - 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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