A monolithic kernel is a kernel where all services (file system, VFS, device drivers, etc) as well as core functionality (scheduling, memory allocation, etc.) are a tight knit group sharing the same space. This directly opposes a microkernel. A microkernel prefers an approach where core functionality is isolated from system services and device drivers (which … Read more
Maximum number of connections are impacted by certain limits on both client & server sides, albeit a little differently. On the client side: Increase the ephermal port range, and decrease the tcp_fin_timeout To find out the default values: sysctl net.ipv4.ip_local_port_range sysctl net.ipv4.tcp_fin_timeout The ephermal port range defines the maximum number of outbound sockets a host … Read more
A single listening port can accept more than one connection simultaneously. There is a ’64K’ limit that is often cited, but that is per client per server port, and needs clarifying. Each TCP/IP packet has basically four fields for addressing. These are: source_ip source_port destination_ip destination_port <—– client ——> <——— server ————> Inside the TCP … Read more
The Linux kernel has a heavy emphasis on community testing. Typically any developer will test their own code before submitting, and quite often they will be using a development version of the kernel from Linus, or one of the other unstable/development trees for a project relevant to their work. This means they are often testing … Read more
bool exists in the current C – C99, but not in C89/90. In C99 the native type is actually called _Bool, while bool is a standard library macro defined in stdbool.h (which expectedly resolves to _Bool). Objects of type _Bool hold either 0 or 1, while true and false are also macros from stdbool.h. Note, … Read more
They are hint to the compiler to emit instructions that will cause branch prediction to favour the “likely” side of a jump instruction. This can be a big win, if the prediction is correct it means that the jump instruction is basically free and will take zero cycles. On the other hand if the prediction … Read more
This is, in effect, a way to check whether the expression e can be evaluated to be 0, and if not, to fail the build. The macro is somewhat misnamed; it should be something more like BUILD_BUG_OR_ZERO, rather than …ON_ZERO. (There have been occasional discussions about whether this is a confusing name.) You should read … Read more