Messages in this thread | | | Subject | Re: [PATCH v2 0/5] Switch arm64 over to qrwlock | From | Adam Wallis <> | Date | Tue, 10 Oct 2017 14:20:34 -0400 |
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On 10/6/2017 9:34 AM, Will Deacon wrote: > Hi all, > > This is version two of the patches I posted yesterday: > > http://lists.infradead.org/pipermail/linux-arm-kernel/2017-October/534666.html > > I'd normally leave it longer before posting again, but Peter had a good > suggestion to rework the layout of the lock word, so I wanted to post a > version that follows that approach. > > I've updated my branch if you're after the full patch stack: > > git://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git qrwlock > > As before, all comments (particularly related to testing and performance) > welcome! > > Cheers, > > Will > > --->8 > > Will Deacon (5): > kernel/locking: Use struct qrwlock instead of struct __qrwlock > locking/atomic: Add atomic_cond_read_acquire > kernel/locking: Use atomic_cond_read_acquire when spinning in qrwlock > arm64: locking: Move rwlock implementation over to qrwlocks > kernel/locking: Prevent slowpath writers getting held up by fastpath > > arch/arm64/Kconfig | 17 ++++ > arch/arm64/include/asm/Kbuild | 1 + > arch/arm64/include/asm/spinlock.h | 164 +------------------------------- > arch/arm64/include/asm/spinlock_types.h | 6 +- > include/asm-generic/atomic-long.h | 3 + > include/asm-generic/qrwlock.h | 20 +--- > include/asm-generic/qrwlock_types.h | 15 ++- > include/linux/atomic.h | 4 + > kernel/locking/qrwlock.c | 83 +++------------- > 9 files changed, 58 insertions(+), 255 deletions(-) >
Applied on 4.14-rc4, I tested these patches with multiple combinations of readers:writers . These patches help prevent writer starvation in every combination that I tested. Without these patches, when the reader:writer ratio is 2:1, it's trivial for me to see acquisitions of 250:1 (@ 2R:1W).
After applying the qrwlock patches, I see the acquisition ratios level out to around ~1.6:1 (@ 2R:1W), which is quite an improvement.
Thanks Will!
Tested-by: Adam Wallis <awallis@codeaurora.org>
-- Adam Wallis Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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