From: Andreas Dilger Subject: Re: [PATCH 2/3] ext4: Context support Date: Thu, 14 Jun 2012 23:18:36 -0600 Message-ID: References: <1339411562-17100-1-git-send-email-saugata.das@stericsson.com> <201206132043.47962.arnd.bergmann@linaro.org> <20120614020757.GB8226@thunk.org> <201206142155.32009.arnd.bergmann@linaro.org> Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: "Ted Ts'o" , Alex Lemberg , HYOJIN JEONG , Saugata Das , Artem Bityutskiy , Saugata Das , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mmc@vger.kernel.org, patches@linaro.org, venkat@linaro.org, "Luca Porzio (lporzio)" To: Arnd Bergmann Return-path: In-Reply-To: <201206142155.32009.arnd.bergmann@linaro.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 2012-06-14, at 3:55 PM, Arnd Bergmann wrote: > My feeling is that we would actually benefit much more from the > erase block alignment than from the context for the large files. > > I think this is something we can do in the Linaro storage team. > We actually have plans to also put the erase block size in the swap > header, so we should be able to use the same code in mke2fs and mkswap, > and potentially others. What we discussed in the storage team meeting > today is that we start out by making ext4 aware of the erase block > size through the superblock and aligning extents for large files to > erase block boundaries. Note that there are already the s_raid_stride and s_raid_stripe_width, used by the ext4 allocator to align the start and size of allocations on RAID systems. The erase block size would be like s_raid_stride (the minimum amount of data to allocate and write contiguously). I don't know that there is a benefit to having a separate erase block size, since in the end it means the same as s_raid_stride to the allocator - make sure allocations/writes are aligned and sized on multiples of this. Cheers, Andreas