Messages in this thread | | | Subject | Re: [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages | From | David Hildenbrand <> | Date | Mon, 1 Mar 2021 13:59:23 +0100 |
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On 01.03.21 13:57, Oscar Salvador wrote: > On Mon, Mar 01, 2021 at 01:43:00PM +0100, David Hildenbrand wrote: >> Same experiment with ZONE_MOVABLE: >> >> a) Free huge pages: all memory can get unplugged again. >> >> b) Allocated/populated but idle huge pages: all memory can get unplugged >> again. >> >> c) Allocated/populated but all 512 huge pages are read/written in a loop: >> all memory can get unplugged again, but I get a single >> >> [ 121.192345] alloc_contig_range: [180000, 188000) PFNs busy >> >> Most probably because it happened to try migrating a huge page while it was >> busy. As virtio-mem retries on ZONE_MOVABLE a couple of times, it can deal >> with this temporary failure. >> >> >> >> Last but not least, I did something extreme: >> >> ]# cat /proc/meminfo >> MemTotal: 5061568 kB >> MemFree: 186560 kB >> MemAvailable: 354524 kB >> ... >> HugePages_Total: 2048 >> HugePages_Free: 2048 >> HugePages_Rsvd: 0 >> HugePages_Surp: 0 >> >> >> Triggering unplug would require to dissolve+alloc - which now fails when >> trying to allocate an additional ~512 huge pages (1G). >> >> >> As expected, I can properly see memory unplug not fully succeeding. + I get >> a fairly continuous stream of >> >> [ 226.611584] alloc_contig_range: [19f400, 19f800) PFNs busy >> ... >> >> But more importantly, the hugepage count remains stable, as configured by >> the admin (me): >> >> HugePages_Total: 2048 >> HugePages_Free: 2048 >> HugePages_Rsvd: 0 >> HugePages_Surp: 0 > > Thanks for giving it a spin David, that is highly appreciated ;-)! > > I will add above information in next's version changelog if you do not mind, > so the before-and-after can be seen clearly. > > I shall send v4 in the course of the next few days. >
I'll have some review feedback on error handling that might be improved, I'll share that shortly.
-- Thanks,
David / dhildenb
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