On 08/29/2016 04:49 PM, Anshuman Khandual wrote: > On 08/29/2016 12:01 PM, Aaron Lu wrote: >> The global zero page is used to satisfy an anonymous read fault. If >> THP(Transparent HugePage) is enabled then the global huge zero page is used. >> The global huge zero page uses an atomic counter for reference counting >> and is allocated/freed dynamically according to its counter value. >> >> CPU time spent on that counter will greatly increase if there are >> a lot of processes doing anonymous read faults. This patch proposes a >> way to reduce the access to the global counter so that the CPU load >> can be reduced accordingly. >> >> To do this, a new flag of the mm_struct is introduced: MMF_USED_HUGE_ZERO_PAGE. >> With this flag, the process only need to touch the global counter in >> two cases: >> 1 The first time it uses the global huge zero page; >> 2 The time when mm_user of its mm_struct reaches zero. >> >> Note that right now, the huge zero page is eligible to be freed as soon >> as its last use goes away. With this patch, the page will not be >> eligible to be freed until the exit of the last process from which it >> was ever used. >> >> And with the use of mm_user, the kthread is not eligible to use huge >> zero page either. Since no kthread is using huge zero page today, there >> is no difference after applying this patch. But if that is not desired, >> I can change it to when mm_count reaches zero. >> >> Case used for test on Haswell EP: >> usemem -n 72 --readonly -j 0x200000 100G > > Is this benchmark publicly available ? Does not seem to be this one > https://github.com/gnubert/usemem.git, Does it ? Sorry, forgot to attach its link. It's this one: https://git.kernel.org/cgit/linux/kernel/git/wfg/vm-scalability.git And the above mentioned usemem is: https://git.kernel.org/cgit/linux/kernel/git/wfg/vm-scalability.git/tree/usemem.c Regards, Aaron -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>