[Xen-ia64-devel] [PATCH][RFC] performance tuning TAKE 4

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Hi all

These patches are for performance tuning TAKE 4.
They are for comment, review and evaluation.
NOTE: tlb flush clock is experimental and unstable. the patch is
      for comments/discussion. Don't apply this patch for evaluation.

PATCHES:
- performace counter
- p2m exposure
- per vcpu vhpt
- tlb tracking
  - grant table transfer 
  - netback skbuff preregister
  - netfront page preregister
- deferred page freeing
- tlb flush clock
  EXPERIMENTAL: this patch causes system very unstable.

CHANGES:
- grant table transfer
  added the functionality to track socket buffer of netback and
  fragment page of netfront.

PATCH DETAIL:
- per vcpu vhpt
  It focuses on vcpu migration between physical cpus.
  With credit scheduler, vcpu is heavily migrated.
  This patch tries to reduce vTLB flush when vcpu is migrated.

- p2m exposure
  DMA paravirtualization requires the conversion from pseudo physical address
  to machine address. Currently it is done by hypercall.
  This patch tries to reduce the conversion overhead by read-only 
  mapping the xen p2m table to domain.

- tlb tracking
  It forcuses on grant table mapping.
  When page is unmapped, full vTLB flush is necessary.
  By tracking tlb insert on grant mapped page, full vTLB flush
  can be avoided.
  Especially vbd does only DMA, so dom0 doesn't insert tlb entry
  on the grant mapped page. In such case any vTLB flush isn't needed.
  
- netback skbuff/netfront page tlb tracking
  This focuses on grant table transfer.
  When page is transfered, full vTLB flush is necessary on both 
  sender domain and receiver domain.
  By preregistering the page, Xen/IA64 begins to track tlb insert on 
  regestered pages.

- deferred page freeing
  When the page in which tlb insert isn't tracked is unmapped/zapped from
  domain, full vTLB flush is necessary again.
  Balloon driver and grant table page transfer is the case.
  This patch focuses on it.
  It tries to batch freeing/zapping page from domain in order
  to reduce full vTLB flush.

- tlb flush clock
  This is intended to be a counter part of Xen/x86 tlb flush clock.
  But I think this causes cpu cache bounces so that this might be
  a bad idea.

thanks.

-- 
yamahata

Attachment: perf-tuning.tar.bz2
Description: Binary data

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