1879814 - Raise network.cache.purgebyfrecency_minprogress_disk/memory values

Status: RESOLVED FIXED

(Core :: Networking: Cache, task, P2)

Description

[Jens Stutte [:jstutte]]

Bug 1875859 added network.cache.purgebyfrecency_minprogress_disk and network.cache.purgebyfrecency_minprogress_memory values to allow PurgeByFrecency to always make some minimal progress if under load but set them to 0 to set a new baseline for its other changes in telemetry.

We want to raise them and see the impact, if any.

Comment 1

[Jens Stutte [:jstutte]]

Attachment: Bug 1879814 - Raise network.cache.purgebyfrecency_minprogress_memory to 32. r?#necko-reviewers

It is hard to predict reasonable values here. Sorting costs n*log2(n) comparisons and refptr swaps where n is the total number of cache entries. If we assume to be able to purge max. 10% of them, sorting a minimum of 32*10 entries takes 320*log2(320) ~= 2660 loop cycles. On the other hand 32 purges translate to probably 64 memory free operations, each of which might write a poison value block of max. 64 bytes each (see bug 1850008), resulting in a total write of 4096 bytes scattered on 64 memory locations plus some overhead for updating the hashtable.
For lower n nothing bad can happen, and for significantly higher n the sorting will always be the heavier part.

Comment 2

[Jens Stutte [:jstutte]]

Attachment: Bug 1879814 - Rename network.cache.purgebyfrecency_minprogress_xxx to network.cache.purge_minprogress_xxx and use it for all purge variants. r?#necko-reviewers

Disk operations are quite expensive, so we just want to do a minimum progress on each invocation.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/24ffc625c71e
Raise network.cache.purgebyfrecency_minprogress_memory to 32. r=necko-reviewers,valentin

Comment 4

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/24ffc625c71e

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/54c13c049873
Rename network.cache.purgebyfrecency_minprogress_xxx to network.cache.purge_minprogress_xxx and use it for all purge variants. r=necko-reviewers,jesup,valentin

Comment 6

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/54c13c049873