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Date: Sat, 19 Aug 2006 16:17:01 -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: Re: [patch] block: fix queue bounce limit calculation In-Reply-To: <200608190612_MC3-1-C895-98A8@...puserve.com> On Sat, 19 Aug 2006 06:11:34 -0400, Chuck Ebbert wrote: > Could this explain reported slowdown on x86_64 after limit was > changed in 2.6.16.7? Oops, I meant 2.6.17.7: | Date: Wed, 2 Aug 2006 13:20:02 -0700 | From: "Robin H. Johnson" <robbat2@...is-terrarum.net> | Subject: 2.6.17.7 leading to doubling system CPU usage? | To: linux-kernel@...r.kernel.org | Message-ID: <20060802202002.GH31144@...ie-int.orbis-terrarum.net> And the patch only fixes the problem on my CDROM. The system only has 512 MB of RAM, so DMA should always be enabled. I applied the below debugging patch and got this (how do I find the dev for the unknown ones?): # dmesg | fgrep -v debounce | fgrep -B 2 bounce [ 16.971945] Probing IDE interface ide0... [ 17.260734] hda: IC25N060ATMR04-0, ATA DISK drive [ 17.931625] isa bounce pool size: 16 pages [ 17.931672] q = ffff81001da606a0, dma = 1, bounce_pfn = 122608, max = 122608 [ 17.931745] q = ffff81001da606a0, dma = 0, bounce_pfn = 1048575, max = 122608 -- [ 17.932039] Probing IDE interface ide1... [ 18.666664] hdc: MATSHITAUJ-840D, ATAPI CD/DVD-ROM drive [ 19.002080] q = ffff81001da60050, dma = 1, bounce_pfn = 122608, max = 122608 [ 19.002142] q = ffff81001da60050, dma = 1, bounce_pfn = 122608, max = 122608 -- [ 21.726613] KBC0 MSE0 P2P AUDO [ 21.726804] ACPI: (supports S0 S3 S4 S5) [ 21.727335] q = ffff81001db23990, dma = 1, bounce_pfn = 122608, max = 122608 <= unknown dev -- [ 25.001150] EXT3 FS on hda7, internal journal [ 25.001156] EXT3-fs: mounted filesystem with ordered data mode. [ 25.620562] q = ffff81001db23340, dma = 1, bounce_pfn = 122608, max = 122608 <== unknown dev [ 25.620587] q = ffff81001db23340, dma = 0, bounce_pfn = 1048575, max = 122608 -- [ 25.676213] sd 0:0:0:0: Attached scsi disk sda [ 25.692273] sd 0:0:0:0: Attached scsi generic sg0 type 0 [ 25.692372] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 <== sda: [ 25.692396] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 why 14 times??? [ 25.693374] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 [ 25.693394] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 25.693485] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 [ 25.693503] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 25.695692] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 [ 25.695714] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 25.695997] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 [ 25.696015] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 25.696316] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 [ 25.696335] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 25.696416] q = ffff81001db22cf0, dma = 1, bounce_pfn = 122608, max = 122608 [ 25.696434] q = ffff81001db22cf0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 25.699613] usb-storage: device scan complete [ 27.331383] eth0: link up, 100Mbps, full-duplex, lpa 0x45E1 [ 35.361254] q = ffff81001da606a0, dma = 0, bounce_pfn = 1048575, max = 122608 <== hda again ??? [ 35.361289] q = ffff81001da606a0, dma = 0, bounce_pfn = 1048575, max = 122608 [ 35.867099] q = ffff81001da60050, dma = 1, bounce_pfn = 122608, max = 122608 <== hdc again ??? [ 35.867136] q = ffff81001da60050, dma = 1, bounce_pfn = 122608, max = 122608 --- 2.6.17.9-32.orig/block/ll_rw_blk.c +++ 2.6.17.9-32/block/ll_rw_blk.c @@ -651,6 +651,15 @@ void blk_queue_bounce_limit(request_queu q->bounce_gfp = GFP_NOIO | GFP_DMA; q->bounce_pfn = bounce_pfn; } + + printk(KERN_ERR "q = %p, dma = %d, bounce_pfn = %lu, max = %lu\n", + q, dma, bounce_pfn, +#if BITS_PER_LONG == 64 + (unsigned long)(min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT) +#else + blk_max_low_pfn +#endif + ); } EXPORT_SYMBOL(blk_queue_bounce_limit); -- 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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