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Re: [PATCH] LTO streamer reorg - try to reduce WPA memory use
- From: Markus Trippelsdorf <markus at trippelsdorf dot de>
- To: Richard Biener <rguenther at suse dot de>
- Cc: gcc-patches at gcc dot gnu dot org, Jan Hubicka <hubicka at ucw dot cz>
- Date: Wed, 30 Jul 2014 07:51:13 +0200
- Subject: Re: [PATCH] LTO streamer reorg - try to reduce WPA memory use
- Authentication-results: sourceware.org; auth=none
- References: <alpine dot LSU dot 2 dot 11 dot 1407291309570 dot 3531 at zhemvz dot fhfr dot qr> <alpine dot LSU dot 2 dot 11 dot 1407291508480 dot 3531 at zhemvz dot fhfr dot qr>
On 2014.07.29 at 15:10 +0200, Richard Biener wrote:
> On Tue, 29 Jul 2014, Richard Biener wrote:
> > This re-organizes the LTO streamer to do compression transparently
> > in the data-streamer routines (and disables section compression
> > by defaulting to -flto-compression-level=0). This avoids
> > keeping the whole uncompressed sections in memory, only retaining
> > the compressed ones.
> > The downside is that we lose compression of at least the string
> > parts (they are abusing the streaming interface quite awkwardly
> > and doing random-accesses with offsets into the uncompressed
> > section). With a little bit of surgery we can get that back I
> > think (but we'd have to keep the uncompressed piece in memory
> > somewhere which means losing the memory use advantage).
> > Very lightly tested sofar (running lto.exp). I'll try a LTO
> > bootstrap now.
> > I wonder what the change is on WPA memory use for larger
> > projects and what the effect on object file size is.
> Updated patch passing LTO bootstrap (one warning fix) and
> with a memory leak fixed.
Testing with Firefox is impossible at the moment because of PR61885.
One thing I've noticed (before the ICE) is that virtual memory usage is
Address Kbytes RSS Dirty Mode Mapping
0000000000400000 16344 9084 0 r-x-- lto1
00000000013f6000 36 36 28 rw--- lto1
00000000013ff000 1072 276 276 rw--- [ anon ]
00000000034aa000 10154940 1540384 1540384 rw--- [ anon ]
00002acf04af2000 136 136 0 r-x-- ld-2.19.90.so
00002acf04b14000 88 88 88 rw--- [ anon ]
---------------- ------- ------- -------
total kB 12022060 3388396 3377708