On Mon, Jan 22, 2018 at 7:23 AM, Justin Pryzby <pry...@telsasoft.com> wrote: > Consider this shorter, less-severe sounding alternative: > "... (but note that this feature can degrade performance of some > <productname>PostgreSQL</productname> workloads)."
I think the patch looks good now. As Justin mentions, as far as I see the only arguable piece is how strong the language should be against Linux THP. On one hand it can be argued that warning about THP issues is not the job of this patch. On the other hand this patch does say more about THP and Googling does bring up a lot of trouble and advice to disable THP, including: https://www.postgresql.org/message-id/CANQNgOrD02f8mR3Y8Pi=zfsol14rqnqa8hwz1r4rsndlr1b...@mail.gmail.com https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/performance_tuning_guide/s-memory-transhuge The RedHat article above says "However, THP is not recommended for database workloads." I'll leave this to the committer and switch this patch to Ready for Committer. By the way, Fedora 27 does disable THP by default, they deviate from upstream in this regard: [catalin@fedie scripts]$ cat /sys/kernel/mm/transparent_hugepage/enabled always [madvise] never [catalin@fedie scripts]$ grep TRANSPARENT /boot/config-4.14.13-300.fc27.x86_64 CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE=y CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD=y CONFIG_TRANSPARENT_HUGEPAGE=y # CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS is not set CONFIG_TRANSPARENT_HUGEPAGE_MADVISE=y CONFIG_TRANSPARENT_HUGE_PAGECACHE=y When I have some time I'll try to do some digging into history of the Fedora kernel package to see if they provide a rationale for changing the default. That might hint whether it's likely that future RHEL will change as well.