From: Damien Le Moal <damien.lemoal@opensource.wdc.com> To: David Laight <David.Laight@ACULAB.COM>, John Garry <john.garry@huawei.com>, kernel test robot <oliver.sang@intel.com> Cc: Christoph Hellwig <hch@lst.de>, "Martin K. Petersen" <martin.petersen@oracle.com>, LKML <linux-kernel@vger.kernel.org>, Linux Memory Management List <linux-mm@kvack.org>, "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>, "lkp@lists.01.org" <lkp@lists.01.org>, "lkp@intel.com" <lkp@intel.com>, "ying.huang@intel.com" <ying.huang@intel.com>, "feng.tang@intel.com" <feng.tang@intel.com>, "zhengjun.xing@linux.intel.com" <zhengjun.xing@linux.intel.com>, "fengwei.yin@intel.com" <fengwei.yin@intel.com> Subject: Re: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0% regression Date: Wed, 10 Aug 2022 06:57:55 -0700 [thread overview] Message-ID: <b082ed3f-e2de-450f-acc6-9508d7689290@opensource.wdc.com> (raw) In-Reply-To: <c4b45c0e06af473abe17e3471e1bb948@AcuMS.aculab.com> On 2022/08/09 8:16, David Laight wrote: > ... >>>> Without knowing what the device adapter is, hard to say where the problem is. I >>>> suspect that with the patch applied, we may be ending up with a small default >>>> max_sectors value, causing overhead due to more commands than necessary. >>>> >>>> Will check what I see with my test rig. >>> >>> As far as I can see, this patch should not make a difference unless the >>> ATA shost driver is setting the max_sectors value unnecessarily low. >> >> That is my hunch too, hence my question about which host driver is being used >> for this test... That is not apparent from the problem report. > > No one's fallen over the old problem and managed to limit > the number of sectors in a read to the number of sectors > in (IIRC) a 'multi sector' read that uses a single DMA burst? > > Was always a good way of killing disk performance. > > IIRC the maximum number of sectors for an ATA disk transfer is 255. That is for super old pata/ide devices. Modern SATA/AHCI disks can do a lot more than that with NCQ/DMA. The default max_sectors_kb for AHCI connected devices is 1280 KB = 2560 sectors, max_segments = 168 and max_segment_size = 65536 B, which gives a reliable command size of at least 168 * 4096 = 688128 B (1344 sectors) with 4KB page size architectures. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) -- Damien Le Moal Western Digital Research
WARNING: multiple messages have this Message-ID (diff)
From: Damien Le Moal <damien.lemoal@opensource.wdc.com> To: lkp@lists.01.org Subject: Re: [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0% regression Date: Wed, 10 Aug 2022 06:57:55 -0700 [thread overview] Message-ID: <b082ed3f-e2de-450f-acc6-9508d7689290@opensource.wdc.com> (raw) In-Reply-To: <c4b45c0e06af473abe17e3471e1bb948@AcuMS.aculab.com> [-- Attachment #1: Type: text/plain, Size: 1539 bytes --] On 2022/08/09 8:16, David Laight wrote: > ... >>>> Without knowing what the device adapter is, hard to say where the problem is. I >>>> suspect that with the patch applied, we may be ending up with a small default >>>> max_sectors value, causing overhead due to more commands than necessary. >>>> >>>> Will check what I see with my test rig. >>> >>> As far as I can see, this patch should not make a difference unless the >>> ATA shost driver is setting the max_sectors value unnecessarily low. >> >> That is my hunch too, hence my question about which host driver is being used >> for this test... That is not apparent from the problem report. > > No one's fallen over the old problem and managed to limit > the number of sectors in a read to the number of sectors > in (IIRC) a 'multi sector' read that uses a single DMA burst? > > Was always a good way of killing disk performance. > > IIRC the maximum number of sectors for an ATA disk transfer is 255. That is for super old pata/ide devices. Modern SATA/AHCI disks can do a lot more than that with NCQ/DMA. The default max_sectors_kb for AHCI connected devices is 1280 KB = 2560 sectors, max_segments = 168 and max_segment_size = 65536 B, which gives a reliable command size of at least 168 * 4096 = 688128 B (1344 sectors) with 4KB page size architectures. > > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) -- Damien Le Moal Western Digital Research
next prev parent reply other threads:[~2022-08-10 13:58 UTC|newest] Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-08-05 8:05 [ata] 0568e61225: stress-ng.copy-file.ops_per_sec -15.0% regression kernel test robot 2022-08-05 8:05 ` kernel test robot 2022-08-08 14:52 ` Damien Le Moal 2022-08-08 14:52 ` Damien Le Moal 2022-08-09 9:58 ` John Garry 2022-08-09 9:58 ` John Garry 2022-08-09 14:16 ` John Garry 2022-08-09 14:16 ` John Garry 2022-08-09 14:57 ` Damien Le Moal 2022-08-09 14:57 ` Damien Le Moal 2022-08-10 8:33 ` John Garry 2022-08-10 8:33 ` John Garry 2022-08-10 13:52 ` Damien Le Moal 2022-08-10 13:52 ` Damien Le Moal 2022-08-09 14:55 ` Damien Le Moal 2022-08-09 14:55 ` Damien Le Moal 2022-08-09 15:16 ` David Laight 2022-08-09 15:16 ` David Laight 2022-08-10 13:57 ` Damien Le Moal [this message] 2022-08-10 13:57 ` Damien Le Moal 2022-08-12 5:01 ` Oliver Sang 2022-08-12 5:01 ` Oliver Sang 2022-08-12 11:13 ` John Garry 2022-08-12 11:13 ` John Garry 2022-08-12 14:58 ` John Garry 2022-08-12 14:58 ` John Garry 2022-08-16 6:57 ` Oliver Sang 2022-08-16 6:57 ` Oliver Sang 2022-08-16 10:35 ` John Garry 2022-08-16 10:35 ` John Garry 2022-08-16 15:42 ` Damien Le Moal 2022-08-16 15:42 ` Damien Le Moal 2022-08-16 16:38 ` John Garry 2022-08-16 16:38 ` John Garry 2022-08-16 20:02 ` Damien Le Moal 2022-08-16 20:02 ` Damien Le Moal 2022-08-16 20:44 ` John Garry 2022-08-16 20:44 ` John Garry 2022-08-17 15:55 ` Damien Le Moal 2022-08-17 15:55 ` Damien Le Moal 2022-08-17 13:51 ` Oliver Sang 2022-08-17 13:51 ` Oliver Sang 2022-08-17 14:04 ` John Garry 2022-08-17 14:04 ` John Garry 2022-08-18 2:06 ` Oliver Sang 2022-08-18 2:06 ` Oliver Sang 2022-08-18 9:28 ` John Garry 2022-08-18 9:28 ` John Garry 2022-08-19 6:24 ` Oliver Sang 2022-08-19 6:24 ` Oliver Sang 2022-08-19 7:54 ` John Garry 2022-08-19 7:54 ` John Garry 2022-08-20 16:36 ` Damien Le Moal 2022-08-20 16:36 ` Damien Le Moal 2022-08-12 15:41 ` Damien Le Moal 2022-08-12 15:41 ` Damien Le Moal 2022-08-12 17:17 ` John Garry 2022-08-12 17:17 ` John Garry 2022-08-12 18:27 ` Damien Le Moal 2022-08-12 18:27 ` Damien Le Moal 2022-08-13 7:23 ` John Garry 2022-08-13 7:23 ` John Garry 2022-08-16 2:52 ` Oliver Sang 2022-08-16 2:52 ` Oliver Sang
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