On Tue, May 6, 2014 at 12:25 AM, Andi Kleen <a...@firstfloor.org> wrote: > There has been a lot of interest recently to run Linux on very small systems, > like Quark systems. These may have only 2-4MB memory. They are also limited > by flash space. > > One problem on these small system is the size of the network stack. > Currently enabling IPv4 costs about 400k in text, which is prohibitive on > a 2MB system, and very expensive with 4MB. > > There were proposals to instead use LWIP in user space. LWIP with > its socket interface comes in at a bit over 100k overhead per application. > > I maintain that the Linux network stack is actually not that bloated, > it just has a lot of features :-) The goal of this project was to > subset it in a sensible way so that the native kernel stack becomes > competitive with LWIP. > > It turns out that the standard stack has a couple of features that > are not really needed on client systems. Luckily it is also > relatively well modularized, so it becomes possible to stub > out these features at the edge. > > With removing these features we still have a powerful TCP/IP stack, > but one that fits better into small systems. > > It would have been prohibitive to ifdef every optional feature. > This patchkit relies heavily on LTO to effectively remove unused > code. This allows to disable features only at the module boundaries, > and rely on the compiler to drop unreferenced code and data. > > A few features have been also reimplemented in a simpler way. > And I shrank a number of data structures based on CONFIG_BASE_SMALL. > > With these changes I can get a fully featured network stack down > to about 170k with LTO. Without LTO there are also benefits, > but somewhat less. > > There are essentially three sensible configurations: > - Full featured like today. > - Client only subset, but still works with standard distribution userland. > Remove some obscure features like fastopen, make all tables smaller, > packet socket mmap code, use a simpler routing table, remove > high speed networking features like RPX, XPS, GRO offload. > Disable SNMP, TCP metrics > - Minimal subset for deeply embedded systems that can use special userland. > Remove rtnetlink (ioctl only), remove ethtool, raw sockets. > > Right now I'm using own Kconfigs for every removed features. I realize > this somewhat increases the compile test matrix. It would be possible > to hide some of the options and select them using higher level > configurations like the ones listed above. I haven't done this > in this version. > > At this point I'm mainly interested in review and comments. > > Git trees: > > git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc net/debloat > Main tree > > git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-misc net/debloat-3.14 > 3.14 based tree. > > Thanks to Tom Zanussi for contributions and testing.
What kind of userspace do you use on such a small system? It looks like you run kernels without procfs and netlink, so not even ps would work. :) -- Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
