Speed up detach by reducing translation retries #4232
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derekbruening
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Dec 15, 2022
Adds new labels delimiting clean call sequences. Converts into a translation record flag when storing translations. Uses the new labels and flag to precisely identify clean call mangling, replacing the previous scheme which incorrectly thought mangled tool pc-relative was a clean call, resulting in incorrect translations and crashes. Adds a test case to api.detach_state by adding a client (by converting it to use static DR) which inserts a pc-relative load. This reproduces the crash on detach, and is fixed with this fix. The added instrumentation caused periodic detach failures which were solved by setting the translation and adding a restore-state event: i#4232 covers trying to improve the situation. Issue: #5786, #4232 Fixes #5786
derekbruening
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Jan 14, 2023
Adds new labels delimiting clean call sequences. Converts into a translation record flag when storing translations. Uses the new labels and flag to precisely identify clean call mangling, replacing the previous scheme which incorrectly thought mangled tool pc-relative was a clean call, resulting in incorrect translations and crashes. Adds a test case to api.detach_state by adding a client (by converting it to use static DR) which inserts a pc-relative load. This reproduces the crash on detach, and is fixed with this fix. The added instrumentation caused periodic detach failures which were solved by setting the translation and adding a restore-state event: i#4232 covers trying to improve the situation. Adds a new instr_t.offset field. Stops using instr_t.note to hold encoding offsets for pc-releative operands. Adds a new field instr_t.offset which is used for this purpose. This leaves note values in place across encodings, which is needed for new clean call marking labels and also simplifies rseq handling code. This instr_t field is a compatibility break and we bump the version and OLDEST_COMPATIBLE_VERSION here to 990. Updates dr_get_note docs. Augments logging of xl8 info with new flag info. Reduces DR_NOTE_FIRST_RESERVED to give DR more reserved labels. This is another compatibility break, while at it. Fixes several issues hit in tests that happened to trigger on the heap bucket size and other changes: + Fixes a rank order violation at loglevel 5: xref #1649 + Writes real xstate_bv into signal frame when setting the xstate context to avoid lazy AVX restore problems. + Tweaks the thread_churn test to work around non-linearities. Issue: #5786, #4232 Fixes #5786
dolanzhao
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Jan 30, 2023
Adds new labels delimiting clean call sequences. Converts into a translation record flag when storing translations. Uses the new labels and flag to precisely identify clean call mangling, replacing the previous scheme which incorrectly thought mangled tool pc-relative was a clean call, resulting in incorrect translations and crashes. Adds a test case to api.detach_state by adding a client (by converting it to use static DR) which inserts a pc-relative load. This reproduces the crash on detach, and is fixed with this fix. The added instrumentation caused periodic detach failures which were solved by setting the translation and adding a restore-state event: i#4232 covers trying to improve the situation. Adds a new instr_t.offset field. Stops using instr_t.note to hold encoding offsets for pc-releative operands. Adds a new field instr_t.offset which is used for this purpose. This leaves note values in place across encodings, which is needed for new clean call marking labels and also simplifies rseq handling code. This instr_t field is a compatibility break and we bump the version and OLDEST_COMPATIBLE_VERSION here to 990. Updates dr_get_note docs. Augments logging of xl8 info with new flag info. Reduces DR_NOTE_FIRST_RESERVED to give DR more reserved labels. This is another compatibility break, while at it. Fixes several issues hit in tests that happened to trigger on the heap bucket size and other changes: + Fixes a rank order violation at loglevel 5: xref #1649 + Writes real xstate_bv into signal frame when setting the xstate context to avoid lazy AVX restore problems. + Tweaks the thread_churn test to work around non-linearities. Issue: #5786, #4232 Fixes #5786
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Separating out from #4219 which is about correctness problems.
With the stats from PR #4228 on a large ~600-thread app under drcachesim, I observed ~500 retries (40x more than plain DR) on detach, and a detach time increase of >2x vs plain DR. This issue trying to reduce that by adding translation handling for more suspend locations so we don't have to retry to suspend.
Xref #37, #38 on ptrace attach/detach which might also speed things up vs signals.
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