memfd: Reduce some syscalls in the on-demand case #3757
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This tweaks the internal organization of the `MemFdSlot` to avoid some syscalls in the default case as well as opportunistically in the pooling case. The two cases added here are: * A `MemFdSlot` is now created with a specified initial size. For pooling this is 0 but for the on-demand case this can be non-zero. * When `instantiate` is called with no prior image and the sizes match (as will be the case for on-demand allocation) then `mprotect` is skipped entirely. * In the `clear_and_remain-ready` case the `mprotect` is skipped if the heap wasn't grown at all. This should avoid ever using `mprotect` unnecessarily and makes the ranges we `mprotect` a bit smaller as well.
cfallin
approved these changes
Feb 2, 2022
mpardesh
pushed a commit
to avanhatt/wasmtime
that referenced
this pull request
Mar 17, 2022
) * memfd: Reduce some syscalls in the on-demand case This tweaks the internal organization of the `MemFdSlot` to avoid some syscalls in the default case as well as opportunistically in the pooling case. The two cases added here are: * A `MemFdSlot` is now created with a specified initial size. For pooling this is 0 but for the on-demand case this can be non-zero. * When `instantiate` is called with no prior image and the sizes match (as will be the case for on-demand allocation) then `mprotect` is skipped entirely. * In the `clear_and_remain-ready` case the `mprotect` is skipped if the heap wasn't grown at all. This should avoid ever using `mprotect` unnecessarily and makes the ranges we `mprotect` a bit smaller as well. * Review comments * Tweak allow to apply to whole crate
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This tweaks the internal organization of the
MemFdSlotto avoid somesyscalls in the default case as well as opportunistically in the pooling
case. The two cases added here are:
A
MemFdSlotis now created with a specified initial size. Forpooling this is 0 but for the on-demand case this can be non-zero.
When
instantiateis called with no prior image and the sizes match(as will be the case for on-demand allocation) then
mprotectisskipped entirely.
In the
clear_and_remain-readycase themprotectis skipped if theheap wasn't grown at all.
This should avoid ever using
mprotectunnecessarily and makes theranges we
mprotecta bit smaller as well.