Type of Talk: GRACS Speaker Series

Speaker/Affiliation:
Donald Porter/University of Texas at Austin

Date/Time: Tuesday, Apr

il 6, 2010, 2:00 p.m.

Location: ACES 2.402

Host: GRACS

Talk Title: Operating System Transactions

Talk Abstract:

Appli

cations must be able to synchronize accesses to operating system
resou

rces in order to ensure correctness in the face of concurrency and
sys

tem failures.  We propose system transactions, with which the progra

mmer
specifies atomic updates to heterogeneous system resources and th

e OS
guarantees atomicity, consistency, isolation, and durability (

ACID).  System
transactions efficiently and cleanly solve persis

tent concurrency problems
that are difficult to address with other tec

hniques.  For example, system
transactions eliminate security v

ulnerabilities in the file system that are
caused by time-of-check-to-

time-of-use (TOCTTOU) race conditions.  System
transactions roll
back an unsuccessful software installation without
disturbing concurr

ent, independent updates to the file system.

This practice job

talk describes TxOS, a variant of Linux 2.6.22 that
implements system
transactions.  The work contributes new implementation
techniqu

es that provide fast, serializable transactions with strong
isolation
and fairness between system transactions and non-transactional
activi

ty.  TxOS demonstrates that a mature OS running on commodity hardware

can provide system transactions at a reasonable performance cost.

This work also shows that system transactions can be used to build<

br />applications with better performance, stronger correctness guarantees
from
simpler code, or both.  For instance, wrapping an instal

lation of OpenSSH in
a system transaction guarantees that a failed ins

tallation will be rolled
back completely.  These atomicity prope

rties are provided by the OS,
requiring no modification to the instal

ler itself and adding only 10%
performance overhead.  System tra

nsactions also minimize non-transactional
overheads, as a non-transac

tional compilation of Linux incurs negligible
overhead on TxOS.

Speaker Bio:

Donald Porter is a Ph.D. student in computer science at

The University of
Texas at Austin.  His research interests inclu

de operating systems,
concurrent programming, and security.  D

onald has published in SOSP, ISPASS,
PLDI, CCS, ISCA, CACM, and

IEEE Micro''s Top Picks issue.  His thesis advisor
is Emmett Wit

chel.  Donald earned an MS in computer science from UT Austin
an

d a BA in computer science and mathematics from Hendrix College.

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