1 / 13

Partial Snapshots

Partial Snapshots. Hagit Attiya (CS, Technion) Joint work with Rachid Guerraoui (EPFL) Eric Ruppert (York University). Taking a Full Snapshot. n components Update a single component Scan all the components “at once” (atomically) Provides an instantaneous view of the whole memory.

dsager
Download Presentation

Partial Snapshots

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Partial Snapshots Hagit Attiya (CS, Technion) Joint work with Rachid Guerraoui (EPFL) Eric Ruppert (York University)

  2. Taking a Full Snapshot n components Update a single component Scan all the components “at once” (atomically) Provides an instantaneous view of the whole memory update scan v1,…,vn ok SPAA

  3. Taking a Partial Snapshot n components Update a single component Scan components “at once” (atomically) Allows to read parts of the memory Worthwhile if we can do it more efficiently than a (full) scan update scan vi1,…,vir ok SPAA

  4. Partial Snapshots: Non-Terminating Algorithm [Afek, Attiya, Dolev, Gafni, Merritt, Shavit, JACM 1993] double collect Update(v,k) A[k] = v,seqi,i • PartialScan() • repeat • read A[i1],…,A[ir] • read A[i1],…,A[ir] • if equal • return A[i1,…,ir] • Linearize: • Updates with their writes • Scans inside the double collects SPAA

  5. Termination? Hat tip [Ellen, Fatuoruo, Ruppert] • Embed a scan within the Update. Update(v,k) V = FullScan A[k] = v,seqi,i,V • PartialScan() • repeat • read A[i1],…,A[ir] • read A[i1],…,A[ir] • if equal • return A[i1,…,ir] • if 2 values in same component • return Vj direct scan • Linearize: • Updates with their writes • Direct scans as before • Borrowed scans in place borrowedscan SPAA

  6. More Efficient Update • Scan only components needed for overlapping scans • But how to know what these are? Active set object: Tracks processes inthe execution [Afek, Stupp, Touitou] join leave getSet ok ok S active set SPAA

  7. p.join ok p.leave ok q.getSet {… …} {…,p,…} More Efficient Update • Scan only components needed for overlapping scans • But how to know what these are? Active set object: Tracks processes inthe execution [Afek, Stupp, Touitou] active set SPAA

  8. Partial Scans w/ Active Set Update(v,k) V = EmbeddedScan() A[k] = v,seqi,i,V • PartialScan() • announce {i1, …, ir} • join • repeat • read A[i1],…,A[ir] • read A[i1],…,A[ir] • ... • leave SPAA

  9. Partial Scans w/ Active Set Update(v,k) V = EmbeddedScan() A[k] = v,seqi,i,V • EmbbededScan() • getSet • read components • repeat • double collect needed components • ... • if 3 different values in same component • borrow the view SPAA

  10. New Active Set Algorithm To join …. last p 16 17 SPAA

  11. New Active Set Algorithm To leave GetSet reads the array ignoring empty locations …. ….,17, last p 16 17 SPAA

  12. Why in the TM Session? • I need to catch a flight at 17h25 • Partial snapshots are very restricted transactions • PartialScan read-only transaction • Update  transaction writing to a single location • Understanding them provides a handle on the inherent cost of TM implementations SPAA

  13. Wrap-Up • A new object: partial snapshot • Obvious applications • Implications for TM • Suggested an approach for solving it using an active set object • New active set algorithms? Esp., less space. • Will have applications to adaptive algorithms. • Better algorithms? Lower bounds? SPAA

More Related