From: John Garry <john.garry@huawei.com>
To: Bart Van Assche <bvanassche@acm.org>,
<damien.lemoal@opensource.wdc.com>, <joro@8bytes.org>,
<will@kernel.org>, <jejb@linux.ibm.com>,
<martin.petersen@oracle.com>, <hch@lst.de>,
<m.szyprowski@samsung.com>, <robin.murphy@arm.com>
Cc: <linux-scsi@vger.kernel.org>, <linux-doc@vger.kernel.org>,
<liyihang6@hisilicon.com>, <linux-kernel@vger.kernel.org>,
<linux-ide@vger.kernel.org>, <iommu@lists.linux-foundation.org>
Subject: Re: [PATCH v3 2/4] dma-iommu: Add iommu_dma_opt_mapping_size()
Date: Wed, 8 Jun 2022 18:39:10 +0100 [thread overview]
Message-ID: <ffc15010-3283-7761-c534-7b226f46d79a@huawei.com> (raw)
In-Reply-To: <d7a72f92-15c9-1d58-c711-83c47444094e@acm.org>
On 08/06/2022 18:26, Bart Van Assche wrote:
> On 6/6/22 02:30, John Garry via iommu wrote:
>> +unsigned long iova_rcache_range(void)
>> +{
>> + return PAGE_SIZE << (IOVA_RANGE_CACHE_MAX_SIZE - 1);
>> +}
>
> My understanding is that iova cache entries may be smaller than
> IOVA_RANGE_CACHE_MAX_SIZE and hence that even if code that uses the DMA
> mapping API respects this limit that a cache miss can still happen.
Sure, a cache miss may still happen - however once we have stressed the
system for a while then the rcaches fill up and don't fail often, or
often enough to be noticeable compared to not having a cached IOVAs at all.
Thanks,
john
next prev parent reply other threads:[~2022-06-08 17:39 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-06 9:30 [PATCH v3 0/4] DMA mapping changes for SCSI core John Garry
2022-06-06 9:30 ` [PATCH v3 1/4] dma-mapping: Add dma_opt_mapping_size() John Garry
2022-06-08 17:27 ` Bart Van Assche
2022-06-06 9:30 ` [PATCH v3 2/4] dma-iommu: Add iommu_dma_opt_mapping_size() John Garry
2022-06-08 17:26 ` Bart Van Assche
2022-06-08 17:39 ` John Garry [this message]
2022-06-14 13:12 ` John Garry
2022-06-23 8:38 ` John Garry
2022-06-06 9:30 ` [PATCH v3 3/4] scsi: core: Cap shost max_sectors according to DMA optimum mapping limits John Garry
2022-06-08 17:33 ` Bart Van Assche
2022-06-08 17:50 ` John Garry
2022-06-08 21:07 ` Bart Van Assche
2022-06-09 8:00 ` John Garry
2022-06-09 17:18 ` Bart Van Assche
2022-06-09 17:54 ` John Garry
2022-06-09 20:34 ` Bart Van Assche
2022-06-10 15:37 ` John Garry
2022-06-23 8:36 ` John Garry
2022-06-06 9:30 ` [PATCH v3 4/4] libata-scsi: Cap ata_device->max_sectors according to shost->max_sectors John Garry
2022-06-07 22:43 ` [PATCH v3 0/4] DMA mapping changes for SCSI core Bart Van Assche
2022-06-08 10:14 ` John Garry
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