On October 11, 2019 9:03:53 AM GMT+02:00, Jan Hubicka <hubi...@ucw.cz> wrote:
>Hi,
>this patch adds ggc_trim that releases free pages used by GGC memory
>to system. This is useful to reduce memory footprint of WPA streaming:
>WPA streaming ought to not use any more GGC memory (patches in testing
>for that) and trimming the memory makes it available to fork&malloc
>used
>by stream out machinery.
>
>I collected some stats for cc1 for both GGC and heap (using mallinfo).
>Memory footprints are as follows:
>
>After streaming in global stream: 123MB GGC; 25MB of heap.
>After streaming in callgraph : 228MB GGC; 45MB of heap.
>After streaming in summaries : 373MB GGC; 126MB of heap.
>After symbol merging : 348MB GGC; 130MB of heap.
>After IPA-ICF : 501MB GGC; 160MB of heap. (this is all ICF)
>After IPA-CP : 528MB GGC; 163MB of heap.
>After IPA-SRA : 532MB GGC; 163MB of heap.
>After Inline : 644MB GGC; 173MB of heap
> This is after collecting of 118MB of
> garbage and returning 740k to system
> by madvise_dontneed
>After ipa-reference : 644MB GGC; 370MB of heap
> I checked this all goes into the
> bitmaps; I have WIP patch for that
>After releasing summariess : 431MB GGC; 383MB of heap
> Trim releases 43MB by unmap
> and 321MB by madvise_dontneed
>
>At least i learnt new fact about ipa-reference consuming 200MB of
>memory which was not obvious from our detailed mem stats.
>
>I think the lowest hanging fruit after this patch is to add
>malloc_madvise which further reduces footpring and fix ipa-reference.
>Hopefully Martin will do a bit about ipa-icf.
>
>I will dig into what inliner does but it produces a lot of clones so I
>think it is mostly clone and summary duplication. Perhaps we can avoid
>copying some of summaries for inline clones.
>
>In TOP I see about 900MB instead of 1.4GB before WPA streaming starts
>with both ggc_trim and madvise.
>
>Note that I also tried to hack ggc_free to recognize free pages but at
>least in simple implementation it is a loss since it makes ggc_alloc
>more expensive (it needs to bring pages back and add into freelists)
>which hurts stream-in performance.
>
>I think sweeping once per WPA is no problem, it is definitly less than
>1% of WPA time.
>
>Bootstrapped/regtested x86_64-linux, OK?
Ok.
Richard.
> * ggc-page.c (release_pages): Output statistics when !quiet_flag.
> (ggc_collect): Dump later to not interfere with release_page dump.
> (ggc_trim): New function.
> * ggc-none.c (ggc_trim): New.
>
> * lto.c (lto_wpa_write_files): Call ggc_trim.
>Index: ggc-page.c
>===================================================================
>--- ggc-page.c (revision 276707)
>+++ ggc-page.c (working copy)
>@@ -529,7 +529,6 @@ static void clear_page_group_in_use (pag
> #endif
> static struct page_entry * alloc_page (unsigned);
> static void free_page (struct page_entry *);
>-static void release_pages (void);
> static void clear_marks (void);
> static void sweep_pages (void);
> static void ggc_recalculate_in_use_p (page_entry *);
>@@ -1016,6 +1015,8 @@ free_page (page_entry *entry)
> static void
> release_pages (void)
> {
>+ size_t n1 = 0;
>+ size_t n2 = 0;
> #ifdef USING_MADVISE
> page_entry *p, *start_p;
> char *start;
>@@ -1061,6 +1062,7 @@ release_pages (void)
> else
> G.free_pages = p;
> G.bytes_mapped -= mapped_len;
>+ n1 += len;
> continue;
> }
> prev = newprev;
>@@ -1092,6 +1094,7 @@ release_pages (void)
>/* Don't count those pages as mapped to not touch the garbage collector
> unnecessarily. */
> G.bytes_mapped -= len;
>+ n2 += len;
> while (start_p != p)
> {
> start_p->discarded = true;
>@@ -1124,6 +1127,7 @@ release_pages (void)
> }
>
> munmap (start, len);
>+ n1 += len;
> G.bytes_mapped -= len;
> }
>
>@@ -1152,10 +1156,20 @@ release_pages (void)
> *gp = g->next;
> G.bytes_mapped -= g->alloc_size;
> free (g->allocation);
>+ n1 += g->alloc_size;
> }
> else
> gp = &g->next;
> #endif
>+ if (!quiet_flag && (n1 || n2))
>+ {
>+ fprintf (stderr, " {GC");
>+ if (n1)
>+ fprintf (stderr, " released %luk", (unsigned long)(n1 / 1024));
>+ if (n2)
>+ fprintf (stderr, " madv_dontneed %luk", (unsigned long)(n2 / 1024));
>+ fprintf (stderr, "}");
>+ }
> }
>
> /* This table provides a fast way to determine ceil(log_2(size)) for
>@@ -2178,19 +2192,22 @@ ggc_collect (void)
> return;
>
> timevar_push (TV_GC);
>- if (!quiet_flag)
>- fprintf (stderr, " {GC %luk -> ", (unsigned long) G.allocated /
>1024);
> if (GGC_DEBUG_LEVEL >= 2)
> fprintf (G.debug_file, "BEGIN COLLECTING\n");
>
> /* Zero the total allocated bytes. This will be recalculated in the
> sweep phase. */
>+ size_t allocated = G.allocated;
> G.allocated = 0;
>
> /* Release the pages we freed the last time we collected, but didn't
> reuse in the interim. */
> release_pages ();
>
>+ /* Output this later so we do not interfere with release_pages. */
>+ if (!quiet_flag)
>+ fprintf (stderr, " {GC %luk -> ", (unsigned long) allocated /
>1024);
>+
> /* Indicate that we've seen collections at this context depth. */
>G.context_depth_collections = ((unsigned long)1 << (G.context_depth +
>1)) - 1;
>
>@@ -2221,9 +2238,25 @@ ggc_collect (void)
> fprintf (G.debug_file, "END COLLECTING\n");
> }
>
>-/* Assume that all GGC memory is reachable and grow the limits for
>next collection.
>- With checking, trigger GGC so -Q compilation outputs how much of
>memory really is
>- reachable. */
>+/* Return free pages to the system. */
>+
>+void
>+ggc_trim ()
>+{
>+ timevar_push (TV_GC);
>+ G.allocated = 0;
>+ sweep_pages ();
>+ release_pages ();
>+ if (!quiet_flag)
>+ fprintf (stderr, " {GC trimmed to %luk, %luk mapped}",
>+ (unsigned long) G.allocated / 1024,
>+ (unsigned long) G.bytes_mapped / 1024);
>+ timevar_pop (TV_GC);
>+}
>+
>+/* Assume that all GGC memory is reachable and grow the limits for
>next
>+ collection. With checking, trigger GGC so -Q compilation outputs
>how much
>+ of memory really is reachable. */
>
> void
> ggc_grow (void)
>Index: ggc-none.c
>===================================================================
>--- ggc-none.c (revision 276707)
>+++ ggc-none.c (working copy)
>@@ -72,3 +72,8 @@ void
> ggc_grow (void)
> {
> }
>+
>+void
>+ggc_trim (void)
>+{
>+}
>Index: lto/lto.c
>===================================================================
>--- lto/lto.c (revision 276707)
>+++ lto/lto.c (working copy)
>@@ -304,6 +306,7 @@ lto_wpa_write_files (void)
>
> timevar_push (TV_WHOPR_WPA_IO);
>
>+ ggc_trim ();
> /* Generate a prefix for the LTRANS unit files. */
> blen = strlen (ltrans_output_list);
> temp_filename = (char *) xmalloc (blen + sizeof ("2147483648.o"));
