Re: [PATCH v3 1/5] hugetlb: add demote hugetlb page sysfs interfaces
From: Oscar Salvador <osalvador@suse.de>
Date: 2021-10-04 13:02:46
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On Fri, Oct 01, 2021 at 10:52:06AM -0700, Mike Kravetz wrote:
-which function as described above for the default huge page-sized case. +The demote interfaces provide the ability to split a huge page into +smaller huge pages. For example, the x86 architecture supports both +1GB and 2MB huge pages sizes. A 1GB huge page can be split into 512 +2MB huge pages. Demote interfaces are not available for the smallest +huge page size. The demote interfaces are: + +demote_size + is the size of demoted pages. When a page is demoted a corresponding + number of huge pages of demote_size will be created. By default, + demote_size is set to the next smaller huge page size. If there are + multiple smaller huge page sizes, demote_size can be set to any of + these smaller sizes. Only huge page sizes less then the current huge
s/then/than ?
quoted hunk ↗ jump to hunk
static void __init hugetlb_init_hstates(void) { - struct hstate *h; + struct hstate *h, *h2; for_each_hstate(h) { if (minimum_order > huge_page_order(h))@@ -2995,6 +2995,23 @@ static void __init hugetlb_init_hstates(void) /* oversize hugepages were init'ed in early boot */ if (!hstate_is_gigantic(h)) hugetlb_hstate_alloc_pages(h); + + /* + * Set demote order for each hstate. Note that + * h->demote_order is initially 0. + * - We can not demote gigantic pages if runtime freeing + * is not supported. + */ + if (!hstate_is_gigantic(h) || + gigantic_page_runtime_supported()) {
Based on the comment, I think that making the condition explicit looks
better from my point of view.
if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
continue;
quoted hunk ↗ jump to hunk
+ for_each_hstate(h2) { + if (h2 == h) + continue; + if (h2->order < h->order && + h2->order > h->demote_order) + h->demote_order = h2->order; + } + } } VM_BUG_ON(minimum_order == UINT_MAX); }@@ -3235,9 +3252,29 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, return 0; }
-- Oscar Salvador SUSE L3