Messages in this thread | | | Subject | Re: [RFC PATCH] mm/hugetlb: Avoid soft lockup in set_max_huge_pages() | From | hejianet <> | Date | Wed, 27 Jul 2016 09:39:51 +0800 |
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Hi Dave
On 7/26/16 11:58 PM, Dave Hansen wrote: > On 07/26/2016 08:44 AM, Jia He wrote: >> This patch is to fix such soft lockup. I thouhgt it is safe to call >> cond_resched() because alloc_fresh_gigantic_page and alloc_fresh_huge_page >> are out of spin_lock/unlock section. > Yikes. So the call site for both the things you patch is this: > >> while (count > persistent_huge_pages(h)) { > ... >> spin_unlock(&hugetlb_lock); >> if (hstate_is_gigantic(h)) >> ret = alloc_fresh_gigantic_page(h, nodes_allowed); >> else >> ret = alloc_fresh_huge_page(h, nodes_allowed); >> spin_lock(&hugetlb_lock); > and you choose to patch both of the alloc_*() functions. Why not just > fix it at the common call site? Seems like that > spin_lock(&hugetlb_lock) could be a cond_resched_lock() which would fix > both cases. I agree to move the cond_resched() to a common site in set_max_huge_pages(). But do you mean the spin_lock in this while loop can be replaced by cond_resched_lock? IIUC, cond_resched_lock = spin_unlock+cond_resched+spin_lock. So could you please explain more details about it? Thanks.
B.R. Justin > Also, putting that cond_resched() inside the for_each_node*() loop is an > odd choice. It seems to indicate that the loops can take a long time, > which really isn't the case. The _loop_ isn't long, right? >
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