Messages in this thread | | | From | Ross Zwisler <> | Subject | [PATCH 0/3] remove rw_page() from brd, pmem and btt | Date | Fri, 28 Jul 2017 10:56:01 -0600 |
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Dan Williams and Christoph Hellwig have recently expressed doubt about whether the rw_page() interface made sense for synchronous memory drivers [1][2]. It's unclear whether this interface has any performance benefit for these drivers, but as we continue to fix bugs it is clear that it does have a maintenance burden. This series removes the rw_page() implementations in brd, pmem and btt to relieve this burden.
The last existing user of the rw_page interface is the zram driver, and according to the changelog for the patch that added zram_rw_page() that driver does see a clear performance gain:
I implemented the feature in zram and tested it. Test bed was the G2, LG electronic mobile device, whtich has msm8974 processor and 2GB memory.
With a memory allocation test program consuming memory, the system generates swap.
Operating time of swap_write_page() was measured.
-------------------------------------------------- | | operating time | improvement | | | (20 runs average) | | -------------------------------------------------- |with patch | 1061.15 us | +2.4% | -------------------------------------------------- |without patch| 1087.35 us | | --------------------------------------------------
Each test(with paged_io,with BIO) result set shows normal distribution and has equal variance. I mean the two values are valid result to compare. I can say operation with paged I/O(without BIO) is faster 2.4% with confidence level 95%.
These patches have passed ext4 and XFS xfstest regression testing with a memory mode pmem driver (without DAX), with pmem + btt and with brd.
These patches apply cleanly to the current v4.13-rc2 based linux/master.
[1] https://lists.01.org/pipermail/linux-nvdimm/2017-July/011389.html [2] https://www.mail-archive.com/linux-block@vger.kernel.org/msg11170.html
Ross Zwisler (3): btt: remove btt_rw_page() pmem: remove pmem_rw_page() brd: remove brd_rw_page()
drivers/block/brd.c | 10 ---------- drivers/nvdimm/btt.c | 15 --------------- drivers/nvdimm/pmem.c | 21 --------------------- 3 files changed, 46 deletions(-)
-- 2.9.4
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