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 yh2M2/t4 BdxNkxR7KFcJLat4s5TFpzkTdZzyVGMJusDZH8dH8nSb0oKS30ClR/Le+COzUz7HzpJnLcpgTbUIpGn1PZ6pE05w6Sxb+d2z9f2qbLQjmsD6JAuv+wr9jEBQ3Bi5FHahG6H9SlK5Mi0q8OdcB7e8GK4VbpIkyD5cdeFzcX3PxcyQiL3AtoJrJaxwPPtKc9l4bZcfV9+6uMFtdQbTdr5LjJZ5zVL/t4NG5fZ/bkWCdlr1WP4MAGOFnJOhK++MPL5Aj6Ze6qw2xjQylcOV59+BNp+P8nJjFwqDqfidJtlNCBX93a9DZKY4Rlg8S83lUxDYr+qfTx1v4+Yj0A92FmnFXYR+dPhnUt0zn/4dDZsV2QrkFonqTZFRyOiGxKey8eG6me53ch9E/xq8Ld7Irxrhfviww7dtKc4sUruQC4hQOlXOqpGuK0knbwBv80/PlFaqKdVBPlYhcyZiySHu1KjNhEO2rzfETskrxWRkd363+wJKgYiIt4COYahHF3zN1c0En+wklnJ00qiV9/qhZFJMc2RWbUi9DHxpaFPho X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 09/06/23 22:27, Usama Arif wrote: > > > On 06/09/2023 19:10, Mike Kravetz wrote: > > On 09/06/23 12:26, Usama Arif wrote: > > > The new boot flow when it comes to initialization of gigantic pages > > > is as follows: > > > - At boot time, for a gigantic page during __alloc_bootmem_hugepage, > > > the region after the first struct page is marked as noinit. > > > - This results in only the first struct page to be > > > initialized in reserve_bootmem_region. As the tail struct pages are > > > not initialized at this point, there can be a significant saving > > > in boot time if HVO succeeds later on. > > > - Later on in the boot, the head page is prepped and the first > > > HUGETLB_VMEMMAP_RESERVE_SIZE / sizeof(struct page) - 1 tail struct pages > > > are initialized. > > > - HVO is attempted. If it is not successful, then the rest of the > > > tail struct pages are initialized. If it is successful, no more > > > tail struct pages need to be initialized saving significant boot time. > > > > Code looks reasonable. Quick question. > > > > On systems where HVO is disabled, we will still go through this new boot > > flow and init hugetlb tail pages later in boot (gather_bootmem_prealloc). > > Correct? > > If yes, will there be a noticeable change in performance from the current > > flow with HVO disabled? My concern would be allocating a large number of > > gigantic pages at boot (TB or more). > > > > Thanks for the review. > > The patch moves the initialization of struct pages backing hugepage from > reserve_bootmem_region to a bit later on in the boot to > gather_bootmem_prealloc. When HVO is disabled, there will be no difference > in time taken to boot with or without this patch series, as 262144 struct > pages per gigantic page (for x86) are still going to be initialized, just in > a different place. I seem to recall that 'normal' deferred struct page initialization was done in parallel as the result of these series: https://lore.kernel.org/linux-mm/20171013173214.27300-1-pasha.tatashin@oracle.com/ https://lore.kernel.org/linux-mm/20200527173608.2885243-1-daniel.m.jordan@oracle.com/#t and perhaps others. My thought is that we lose that parallel initialization when it is being done as part of hugetlb fall back initialization. Does that make sense? Or am I missing something? I do not have any proof that things will be slower. That is just something I was thinking about. -- Mike Kravetz