tree a77acab781422c0c3d0ee29ccef5a16a169b1c83
parent cc542e56256b2e5fc41aab92537b965568244c85
author Kostya Kortchinsky <kostyak@google.com> 1592415113 -0700
committer Copybara-Service <copybara-worker@google.com> 1598597919 -0700

[scudo][standalone] Release smaller blocks less often

Summary:
Releasing smaller blocks is costly and only yields significant
results when there is a large percentage of free bytes for a given
size class (see numbers below).

This CL introduces a couple of additional checks for sizes lower
than 256. First we want to make sure that there is enough free bytes,
relatively to the amount of allocated bytes. We are looking at 8X% to
9X% (smaller blocks require higher percentage). We also want to make
sure there has been enough activity with the freelist to make it
worth the time, so we now check that the bytes pushed to the freelist
is at least 1/16th of the allocated bytes for those classes.

Additionally, we clear batches before destroying them now - this
could have prevented some releases to occur (class id 0 rarely
releases anyway).

Here are the numbers, for about 1M allocations in multiple threads:

Size: 16
85% freed -> 0% released
86% freed -> 0% released
87% freed -> 0% released
88% freed -> 0% released
89% freed -> 0% released
90% freed -> 0% released
91% freed -> 0% released
92% freed -> 0% released
93% freed -> 0% released
94% freed -> 0% released
95% freed -> 0% released
96% freed -> 0% released
97% freed -> 2% released
98% freed -> 7% released
99% freed -> 27% released
Size: 32
85% freed -> 0% released
86% freed -> 0% released
87% freed -> 0% released
88% freed -> 0% released
89% freed -> 0% released
90% freed -> 0% released
91% freed -> 0% released
92% freed -> 0% released
93% freed -> 0% released
94% freed -> 0% released
95% freed -> 1% released
96% freed -> 3% released
97% freed -> 7% released
98% freed -> 17% released
99% freed -> 41% released
Size: 48
85% freed -> 0% released
86% freed -> 0% released
87% freed -> 0% released
88% freed -> 0% released
89% freed -> 0% released
90% freed -> 0% released
91% freed -> 0% released
92% freed -> 0% released
93% freed -> 0% released
94% freed -> 1% released
95% freed -> 3% released
96% freed -> 7% released
97% freed -> 13% released
98% freed -> 27% released
99% freed -> 52% released
Size: 64
85% freed -> 0% released
86% freed -> 0% released
87% freed -> 0% released
88% freed -> 0% released
89% freed -> 0% released
90% freed -> 0% released
91% freed -> 0% released
92% freed -> 1% released
93% freed -> 2% released
94% freed -> 3% released
95% freed -> 6% released
96% freed -> 11% released
97% freed -> 20% released
98% freed -> 35% released
99% freed -> 59% released
Size: 80
85% freed -> 0% released
86% freed -> 0% released
87% freed -> 0% released
88% freed -> 0% released
89% freed -> 0% released
90% freed -> 1% released
91% freed -> 1% released
92% freed -> 2% released
93% freed -> 4% released
94% freed -> 6% released
95% freed -> 10% released
96% freed -> 17% released
97% freed -> 26% released
98% freed -> 41% released
99% freed -> 64% released
Size: 96
85% freed -> 0% released
86% freed -> 0% released
87% freed -> 0% released
88% freed -> 0% released
89% freed -> 1% released
90% freed -> 1% released
91% freed -> 3% released
92% freed -> 4% released
93% freed -> 6% released
94% freed -> 10% released
95% freed -> 14% released
96% freed -> 21% released
97% freed -> 31% released
98% freed -> 47% released
99% freed -> 68% released
Size: 112
85% freed -> 0% released
86% freed -> 1% released
87% freed -> 1% released
88% freed -> 2% released
89% freed -> 3% released
90% freed -> 4% released
91% freed -> 6% released
92% freed -> 8% released
93% freed -> 11% released
94% freed -> 16% released
95% freed -> 22% released
96% freed -> 30% released
97% freed -> 40% released
98% freed -> 55% released
99% freed -> 74% released
Size: 128
85% freed -> 0% released
86% freed -> 1% released
87% freed -> 1% released
88% freed -> 2% released
89% freed -> 3% released
90% freed -> 4% released
91% freed -> 6% released
92% freed -> 8% released
93% freed -> 11% released
94% freed -> 16% released
95% freed -> 22% released
96% freed -> 30% released
97% freed -> 40% released
98% freed -> 55% released
99% freed -> 74% released
Size: 144
85% freed -> 1% released
86% freed -> 2% released
87% freed -> 3% released
88% freed -> 4% released
89% freed -> 6% released
90% freed -> 7% released
91% freed -> 10% released
92% freed -> 13% released
93% freed -> 17% released
94% freed -> 22% released
95% freed -> 28% released
96% freed -> 37% released
97% freed -> 47% released
98% freed -> 61% released
99% freed -> 78% released
Size: 160
85% freed -> 1% released
86% freed -> 2% released
87% freed -> 3% released
88% freed -> 4% released
89% freed -> 5% released
90% freed -> 7% released
91% freed -> 10% released
92% freed -> 13% released
93% freed -> 17% released
94% freed -> 22% released
95% freed -> 28% released
96% freed -> 37% released
97% freed -> 47% released
98% freed -> 61% released
99% freed -> 78% released
Size: 176
85% freed -> 2% released
86% freed -> 3% released
87% freed -> 4% released
88% freed -> 6% released
89% freed -> 7% released
90% freed -> 9% released
91% freed -> 12% released
92% freed -> 15% released
93% freed -> 20% released
94% freed -> 25% released
95% freed -> 32% released
96% freed -> 40% released
97% freed -> 51% released
98% freed -> 64% released
99% freed -> 80% released
Size: 192
85% freed -> 4% released
86% freed -> 5% released
87% freed -> 6% released
88% freed -> 8% released
89% freed -> 10% released
90% freed -> 13% released
91% freed -> 16% released
92% freed -> 20% released
93% freed -> 24% released
94% freed -> 30% released
95% freed -> 37% released
96% freed -> 45% released
97% freed -> 55% released
98% freed -> 68% released
99% freed -> 82% released
Size: 224
85% freed -> 8% released
86% freed -> 10% released
87% freed -> 12% released
88% freed -> 14% released
89% freed -> 17% released
90% freed -> 20% released
91% freed -> 23% released
92% freed -> 28% released
93% freed -> 33% released
94% freed -> 39% released
95% freed -> 46% released
96% freed -> 53% released
97% freed -> 63% released
98% freed -> 73% released
99% freed -> 85% released
Size: 240
85% freed -> 8% released
86% freed -> 10% released
87% freed -> 12% released
88% freed -> 14% released
89% freed -> 17% released
90% freed -> 20% released
91% freed -> 23% released
92% freed -> 28% released
93% freed -> 33% released
94% freed -> 39% released
95% freed -> 46% released
96% freed -> 54% released
97% freed -> 63% released
98% freed -> 73% released
99% freed -> 85% released

Reviewers: cferris, pcc, hctim, eugenis

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D82031

GitOrigin-RevId: 79de8f8441d12b715b6616dde4b8b15507b88324