Messages in this thread | | | Date | Mon, 13 Sep 2010 20:40:16 +0200 | Subject | Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation | From | Stephane Eranian <> |
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On Mon, Sep 13, 2010 at 7:35 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Mon, 2010-09-13 at 17:55 +0200, Stephane Eranian wrote: >> >> Ok, so you're saying there is no allocator that will give non-contiguous >> physical memory WITHOUT requiring a page fault to populate the pte. >> >> On the other hand, with vmalloc_node() the pte are populated when >> you first touch the memory. That happens as part of memset() right after >> the allocation and thus outside of NMI interrupt handler. >> >> Does this sound right? > > Nope, in particular read: http://lkml.org/lkml/2010/7/14/465 > > The issue is that the vmalloc space can be mapped in different > processes, and that memset() will only ensure its mapped in the current > process, but the next one might need that fault to populate. > Ok, so can we play the same trick you're playing with the sampling buffer, i.e., you use alloc_pages_node() for one page at a time, and then you stitch them on demand via SW?
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