Re: [PATCH 01/12] uprobes: split THPs before trying replace them

From: Srikar Dronamraju
Date: Wed Jan 25 2017 - 21:54:40 EST

> >
> > The first time the breakpoint is hit on a page, it replaces the text
> > page with anon page. Now lets assume we insert breakpoints in all the
> > pages in a range. Here each page is individually replaced by a non THP
> > anonpage. (since we dont have bulk breakpoint insertion support,
> > breakpoint insertion happens one at a time). Now the only interesting
> > case may be when each of these replaced pages happen to be physically
> > contiguous so that THP kicks in to replace all of these pages with one
> > THP page. Can happen in practice?
> >
> > Are there any other cases that I have missed?
> We use a hack in our applications where we open /proc/self/maps, copy
> text segments to a staging area, then create overlay anon mappings on
> top and copy the text back into them. Now we have THP-backed text and
> very little iTLB pressure :-)
> That said, we haven't run into the uprobes issue yet.

Thanks Johannes, Kirill, Rik.

Reviewed-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>